Chase rules

First non-session log post in ages! I'm going to run a city campaign for/about a bunch of thieves, and I wanted to offer more explicit options to resolve situations than fighting, bluffing and stealth. Here's the chase system I'll be using; a slightly tweaked Night's Black Agents with encounters for a bog standard low-magic medieval fantasy setting.

Chase scenes are about outwitting and outrunning your opponent. They should be frantic, vivd, fast-paced. And everybody in the group should be able to contribute. I want to run this off the cuff, which means I don't want to micro-manage and plan out every last little obstacle, juggle movement speeds per character, initiative, opportunity attacks and so on.

Eberron skycoach chase in Sharn

I'll run chases as extended opposed skill checks. Yes, it's a reviled D&D 4e mechanic, yes we'll make it work anyway. My goal is a fast movie montage of cool situations and quick decisions, not endless fiddling with modifiers. I also want variety in the challenges; not just comparing movement speeds, but throwing up situations for the players to navigate in (hopefully) new and exciting ways. I'm choosing a system that treats a group of chasers or runners as one single entity, so that I don't have the hassle of tracking how far ahead each individual is. Speed over detail here.

Night's Black Agents has a perfect little system - I only needed to file off the serial numbers and write up a bunch of obstacles. Rules first, obstacles and persistent conditions at the bottom of the post. This is written for a 5e game in a lowish-magic setting like the City of Lankhmar. In a place with a lot of low level magic like Eberron, spice things up with feather fall tokens, boots of jumping and so on.

Optional rules for those who like more crunch are in italics. They can mostly be used independent of each other.


>> USE THIS CHASE TRACKER FOR D&D 5E [ google doc ] <<

CHASE RULES

Set-up. Runners are the people trying to get away, Chasers are the ones trying to catch them. You track the distance between the two groups in an abstract way using the Lead stat. Runners need to reach a certain Lead to escape, Runners want to reduce that Lead to 0.

• Draw one box for each number of Lead on some scrap paper; track the Runner's Lead with a token like a die, a coin or a mini.
• If you're aiming for immersion, don't show the players the progress track - only describe if they're pulling away, close to getting caught, how close they are to their goal etc.
• If you really need to know exact distances, assign ranges for spells and attacks to different brackets of Lead. Lead 0-2 is 0-60 feet, Lead 3-6 is 60-200 feet, Lead 7-14 is 200-1000 feet.

Lead and Obstacles. The way you change Lead is by going through Obstacles; quick little situations you can navigate in a ton of different ways. Select Obstacles in advance or roll them as you go. Be prepared for a chase to hit the rooftops, sewers, water etc - I've included slightly longer lists for those environments.

The Runner starts with a Lead halfway to their Target, depending on the overall terrain:

• Crowded, twisty alleys, lots of obstacles: start at Lead 3, escape at Lead 6.
  +1 bonus to rolls to the most agile group (highest average Dex), adjust initial Lead by 1 in their favor
• Minor obstacles: start at Lead 5, escape at Lead 10.
  +1 bonus to rolls to the fastest group (highest average Speed), adjust initial Lead by 1 in their favor
• Wide open terrain: start at Lead 7, escape at Lead 14.
  +1 bonus rolls to the group with the best endurance (highest average Con), adjust initial Lead by 1 in their favor
• Initial conditions: ± 1-3 to Lead for an (un)favorable start like being surprised by guards, sabotaging the opponents' cart etc.

Have you tried just walking at street level?

Have the group pick a leader for the round and let them describe their approach. Each group moves as one close-packed group. Every round, another player heads each group and rolls a skill check to try and overcome the Obstacle.

• Every skill is fair game, if the player can describe how they try to use it to navigate the Obstacle. Allow for crazy stunts and reward those in narration. In 5e, you can always give +d6 Inspiration for a really cool idea.
• The base difficulty for the skill check is 13.
• Each round, the head Runner may decide to raise the stakes by upping the Difficulty by 1. They may also keep it at the current level. The Difficulty may only be lowered by 1 (down to 13) when both the head Runner and Pursuer agree. This represents choosing a faster pace, a more difficult route or some other risky stratagem. Ask them to describe how they see this raise looking in the fiction.
• If the lead character wants to use a skill that their group already used before in this chase, up their Difficulty for this roll by 1 - stimulates creative solution.
• Up the difficulty by 1 if a character has headed the roll-off before - this both simulates the group getting tired and stimulates them to let everyone in the group take a turn.

Roll-off. Best roll changes Lead in that group's favor. Describe the results of the rolls, tell your players how close they are to catching or escaping their opponents, and go for the next Obstacle. If the chase is heading in a particular direction (you need to reach the boat / catch the cultist before they reach their safe house), mention how close you're getting.

• Runner fails, Pursuer succeeds: Lead shortens by 2.
• Runner and Pursuer both succeed or fail: Lead changes by 1 according to whose margin was greater. In case of an exact tie, keep the Lead as-is.
• Runner succeeds, Pursuer fails: Lead lengthens by 2.
• If either party rolls a 1, add a Condition and up the Difficulty by 1. (See bottom of post for examples). If either party rolls a 20, they can remove an ongoing Condition and reduce the Difficulty by 1.

The Goblin Chase, by Sean Andrew Murray

RUNNING A CHASE

Pick an Obstacle. Describe quickly what the group sees - this is all happening on the run. First impressions, one big hit of flavor, then boom: who takes point? What do you do?

You'll get questions from your group. Fine, use those to flesh out the scene. Try to keep that to under one minute though, this is about keeping a frantic pace.

Have the head Runner for the group describe their approach and pick a skill for it, then the same for the Pursuers. Describe results: this is going to be chaotic, lean into that. Reward crazy ideas with cool descriptions, then on to the next Obstacle!

THINKING ABOUT OBSTACLES

Ideally, Obstacles are situations that the players can decide to tackle in lots of different ways, not a straightjacket to which there is only one answer. So, "You run into an alley full of street food vendors, with drunks and hot grease everywhere - what do you do?", instead of "there's a closed fence - roll for lock picking!")

My advice is to pick or roll a bunch of Obstacles ahead of time so you can keep up the pace during the chase without having to consult tables all the time. Of course if your group decides to head for the roof tops / into the sewers / back to the streets, you'll need to find appropriate new Obstacles, but it pays to have some pre-selected.

OPTIONAL CHASE RULES

Only recommended if you've got the basic Chase rhythm down.

• One Runner and one Pursuer character may choose to take an action (ranged attack or cast a spell) to try and change the Difficulty for the round. This always raises their group's Difficulty by 1.
  
  For instance, a druid could summon a thicket of brambles to tangle his pursuers and give them +1 Difficulty, or a wizard could cast haste to give his group an ongoing -1 Difficulty. The idea is not to drop into blow-by-blow combat during a Chase - that's what the combat rules are for. Reflect the effect of the player's action in the round's Difficulty and move on.
• Runners can choose to split the party at the start of a new round; the Pursuers then have the option of sticking with one group or splitting up as well. Deception / Insight checks might be necessary if the Runners want to hide which group has the MacGuffin, hostage, etc. (No casting spells or attacks this round; this counts as one character's action - see below.)
• If both groups split up, run this as two separate Leads to close or open up. Botches and Criticals still inflict / alleviate Conditions.
• If the Pursuers stick together, increase the Difficulty for their Runners by +1 to represent them being hounded by a comparatively larger group. The other Runners escape.

• At Lead [target -2] or higher, the Runner may make an additional skill check at Difficulty +2 to make a sudden escape; the lead character decides how they suddenly manage to give their Pursuers the slip. Failure ups their Difficulty by 1 for the rest of the chase. Depending on your system, inflict subdual damage or exhaustion as a cart crashes, ankles are twisted after a long drop and so on. As before, skills used already once before incure a +1 Difficulty, so just spamming "we run extra hard and roll Athletics" is not a winning strategy.
• At Lead 2 or below, the Pursuer may make an additional check at Difficulty +2 to grab the Runner in a final burst of speed. The lead Pursuer describes how this happens and which skill they want to use. Failure ups the Pursuers' Difficulty by 1 for the rest of the chase. Depending on your system, inflict subdual damage or exhaustion.

OBSTACLES

FINALLY, shit to pepper your chase with. Either plan these out ahead of time (so you can foreshadow) or roll as you go along. Sewers and rooftops have longer lists, because face it, your players will go there first chance they get.

Street market (d12)

1. Pottery merchant on obstinate donkey
2. Cart with wine barrels
3. Oil barrels waiting to be carried inside
4. Carpet vendor
5. Street food vendor, lots of grease and hot coals
6. Busy market square
7. Slippery, smelly fish market
8. Porters taking a break, street filled with their haul
9. Stampeding herd animals
10. Escaped flock of poultry and their owner
11. Escaped exotic wild animal, owners shouting not to hurt it
12. Cock or dog fight

A complication (d12)

1. Doom prophet loudly denouncing you to his flock
2. Jugglers and the crowd around them
3. Bar fight spilled into the street
4. Loan shark thinks you owe them
5. Assassins mistake you for their quarry
6. Clandestine drugs sale to noble's servants
7. Frantic victim asking to help escape kidnappers
8. Man begging wife for forgiveness as she throws his stuff out the window
9. Guards sleeping lightly on the job
10. Bunch of prostitutes trying to turn a trick
11. Robbers beating up victim in back alley
12. Murderous black fog out to throttle someone

Crowd (d12)

1. Mimes and living statues, invisible walls & illusionary obstacles
2. Road full of tired, disoriented pilgrims
3. Funeral procession, black robes and lots of chanting
4. Town cryer and group of listeners
5. Priest giving outdoor sermon
6. Bunch of guards saw you running and intercept
7. Marriage ceremony in progress
8. Pickpockets working a crowd - including you
9. Bucket brigade trying to put out burning building
10. Rowdy party-goers spoiling for a fight
11. Workers revolting against unfair taxes
12. Outdoor pub, wooden planks on barrels

Hindrance (d12)

1. Slippery puddle of spilled oil or worse
2. Alley deadends into tanner's worksplace
3. Archway leads to a busy smithy
4. Stairs turn into a bricked up doorway
5. Alchemists guild disposing of acidic waste
6. Inn keeper refusing to take delivery of substandard wine
7. Two cart drivers refusing to give way
8. Magnificent war horse blocks half the road
9. Sedan chair with snooty noble and guards with big sticks
10. Cart pulls out in front of you
11. Idiot bard on horseback weaving across the street
12. Two men very carefully carrying a plate of glass

Geography (d12)

1. Cul-de-sac with rusty gate and closed doors
2. Extremely narrow alley
3. Sudden open square with long lines of sight
4. Collapsed building filling road with rubble
5. Lots of ankle-trapping potholes
6. Dizzying cliff edge, view to lower level
7. Overhanging wrought-iron balcony
8. Run into cliff wall to higher level
9. Narrow, rusted crate to the sewers
10. Open sewer
11. Narrow bridge across a stagnant canal
12. Slippery quay with small boats

On the water (d12)

1. River patrol demands you stop
2. Fat river barge blocking the way
3. Unusually large fish nudging boat
4. Extremely low bridge dead ahead
5. Pleasure boat with raucous party in your way
6. Fishers arguing over whose turn it was to haul the net
7. Swarm of rats climbing into the boat
8. Floating debris blocking fast travel
9. Three nobles in an illicit gathering
10. Drunks pissing into the river, throwing rocks
11. Rope covered in pitch across the water
12. Assassin on the run jumps into boat, demands getaway

In the sewers (d20)

1. Ancient cistern with exits halfway up the smooth walls
2. Thieves exiting torn down wall into a cellar
3. Meeting of Rat cultists
4. Albino alligator drifting past
5. Sudden flood of waste water
6. Marsh gas, liable to explode
7. Gate rusted shut
8. Apprentice trying out some demon summoning
9. Moonshine still with lots of flammable juice
10. Sluice half-closed against the recent heavy rains
11. Spider webs. Thin strands at first, then fat cables and curtains
12. Unstable and slippery wooden plank leads to darkened side tunnel
13. Flood of rats racing to you
14. Three ghouls digging into a private crypt
15. Tunnel lowers to slippery crawlspace
16. Vermin collectors placing traps
17. Underground market with illegal goods
18. Shut-in commune asks gift to open gate
19. Drug runners with a skiff full of green opium
20. Guards with plague masks hunting drug smugglers

Rooftops (d20)

1. Clotheslines, impossible to see past
2. Damaged roof with lots of holes to fall through
3. Red roof tiles that splinter and get slippery in rain
4. Midnight drug users on a rooftop terrace
5. Assassins getting ready for infiltration
6. Rusty drainpipe will break if climbed incautiously
7. Tyaa-bird (intelligent bird or harpy) making its way into a skylight
8. Steep roof over a deep drop
9. Big jump across the street
10. Gusts of biting clouds from below
11. Narrow beam across very wide street
12. Thatched roof, catches your feet, very flammable
13. Large stained glass window in the way; a skylight is open
14. Next roof over is higher than this one
15. Clattering roof tiles alert home owner and their dog
16. Astrologer blocks path with elaborate, fragile telescope
17. Glyph of Warding to ward off burglars on your path
18. Spiky weathervine swinging back and forth
19. Hatch to lower level is bolted from below
20. Surprised smugglers accessing their secret stash

CONDITIONS

When either Pursuers or Runners roll a 1 on their skill check, inflict an ongoing Condition on everyone. If a party rolls a 20, they can choose to end one condition.

Every condition inflicts an ongoing problem on the Runners and Pursuers. The lead character in every group rolls a check against Difficulty every round or the group suffers the effects of one of these ongoing conditions:

• Flash rains block sight, extinguish torches, make everything slippery. Dex save or the group loses 1 Lead.
• Lightning storm disorients everyone with flashes and thunder. Wisdom save or the group loses 1 Lead.
• Fire! A band of arsonists - or cultists? - has set fire to the neighbourhood. Dex save or everyone in the group takes d6 damage.
• CLOUD OF HATRED. A hidden cult has summoned the Cloud of Hate. People riot in the streets. Wisdom save or the group members inflict d6 damage on each other; add +1 to the Difficulty of Obstacles involving people.
• Festival! An obscure faith demands an impromptu celebration. Fireworks, loud trumpets, jostling crowds. Persuasion check or the group loses 1 Lead. 
• The stars are right. Mad visions plague the living. Intelligence save or reroll your chase check.
• All Thieves' Night. Impromptu celebration by the followers of a local thieving god. Perception roll or a random group member loses a small item like a purce, ring or amulet. Any objects the group just stole (probably the reason they're being chased) have a 1-in-6 chance of being stolen this way. If the roll misses by 5 or less, the group realizes the theft and can try to chase the thief. If not, they realize next round and can give chase at a higher Lead.