D&D 5E Melee combat on the run

[Hriston]

The tarrasque runs away. The players decide to have their characters give chase. Why is it inappropriate to transition to chase rules at that time?

Because the chase is over as soon as the PCs catch up with the tarrasque, which is on the very same turn it began.

 

[Asisreo]

I have a huge problem unilaterally moving out of combat rules.

1. Just because one foe is fleeing does not mean the others are. Combat may still be going on.
2. Consistency - if while on the map the party's rogue can keep up with the foe's dash and still attack, why can they suddenly not do the same action on the same creature? There are lots of cases where swapping rules subsystems will favor or hinder withour a corresponding large payout to offset this loss of consistency.
3. Some people may not be chasing, instead they are still in combat using ranged attacks.

Actually, there's nothing in the rules that says combat ends and chases begins. You can have a pursuer and quarry in the same initiative order as combatants as far as I can tell.

 

[Asisreo]

Because the chase is over as soon as the PCs catch up with the tarrasque, which is on the very same turn it began.

The chase is over only when one side drops out of the chase or the Quarry gets away. Getting in melee does jot end a chase sequence. It's 100% possible you're within 5ft of your quarry and he gets away because you get exhausted before he does.

 

[iserith]

Because the chase is over as soon as the PCs catch up with the tarrasque, which is on the very same turn it began.

Though the rules state that the chase ends when the pursuers are close enough to the quarry to catch it, the DM doesn't have to drop out of the chase rules simply because some of the PCs go adjacent to the quarry. Attacks can take place during a chase, just not OAs. Just continue the chase scene as normal.

 

[Ristamar]

It wasn’t really a chase because the monster couldn’t out run the PCs so they could keep up with it and harry it while it was trying to futilely escape with its last few HP. I probably should have ended it earlier but I was waiting for a good moment. Fortunately it happened right after as the weakest PC made a lucky killing shot with their bow.

If you're interested, I've got expanded rules for retreat, evasion, and pursuit (which I'd like to eventually put on the DM's Guild) that build off the existing Chase rules in the DMG . I'd rather not post them for general public consumption as they're currently incomplete, but I can send you a PM of what I've got so far that's workable.

 

[Hriston]

The chase is over only when one side drops out of the chase or the Quarry gets away. Getting in melee does jot end a chase sequence. It's 100% possible you're within 5ft of your quarry and he gets away because you get exhausted before he does.

DMG, p 253, “A chase ends when... the pursuers are close enough to their quarry to catch it.”

 

[Asisreo]

DMG, p 253, “A chase ends when... the pursuers are close enough to their quarry to catch it.”

Whoops, missed that. Though when a chase starts, it's best to not have the players start adjacent to the Quarry. The DM determines the distance and even if it began with them adjacent, a 100-200ft headstart will keep the chase going for a bit.

 

[billd91]

I have a huge problem unilaterally moving out of combat rules.

1. Just because one foe is fleeing does not mean the others are. Combat may still be going on.
2. Consistency - if while on the map the party's rogue can keep up with the foe's dash and still attack, why can they suddenly not do the same action on the same creature? There are lots of cases where swapping rules subsystems will favor or hinder withour a corresponding large payout to offset this loss of consistency.
3. Some people may not be chasing, instead they are still in combat using ranged attacks.

As a DM managing the application of the rules, I don't have any problem unilaterally telling the players we're moving out of traditional combat rules. Though, if one foe is fleeing and others are staying behind as in case 1, that's a different situation and one we're not really talking about here.

But as far as the situation in the OP, I'd have no problem just telling the players, once they decide they're pursuing the fleeing creature, that we're coming out of traditional segmented combat rounds and movement. If they can keep pace, their attacks will occur on their regular initiatives not with segments of movement, attacks, and all that. If that means they miss out on getting attacks of opportunity that would only exist because of the segmented turn structure, I don't really care. If PCs stay behind without chasing, they can still shoot on their initiatives as long as the creature remains in range (which is generally, quite a while if out in the open).
As DM, it's incumbent on me to manage the rules of the game in a way that makes sense for the story of the situation. And if traditional combat rounds and turns don't make much sense, I'll adjust and keep the game working smoothly.

 

[robus]

The tarrasque runs away. The players decide to have their characters give chase. Why is it inappropriate to transition to chase rules at that time?

Because the tarrasque can't outrun the players. They can easily catch it, so there's no chase?

 

[iserith]

Because the tarrasque can't outrun the players. They can easily catch it, so there's no chase?

All that means in my view is that the chase is likely short-lived as compared to a faster creature, not that it's inappropriate to transition to a chase scene using the chase rules. Chasing down and killing a fleeing tarrasque while dealing with complications in its wake is the stuff of exciting, memorable stories. I don't see any downsides here.

Edited to add: Tarrasques can move at 140 ft./round including its Legendary Actions. At least some PCs may not be able to keep up with that pace depending on the party composition. Some may have to spend resources to do so.