But I ask... how much fun is it for players if you as the DM have set up a monster (maybe a boss like above examples but it doesn't have to be) that can engage, fight for a round or two, then pull back to a safe location? Does it make it less fair if it has a way to heal or regen?
now this is 2 different types of sceneros... if it is using resources and getting weaker it is still just a game of attrition... BUT if it can regenerate without cost, it could turn VERY 1 sided.
Does anyone have experence with NPC/Monsters running this way?
This is very interesting.
In running the Vecna battles, his ability to regen 80 hp per round is HUGE, but can be easily countered in battle via
chill touch and other spells. However, if he gets away for just a few rounds, he could potentially be back at full strength in very little time.
Other regenerating creatures can do the same, but might take longer.
Meanwhile, the PCs have to use (limited) resources to "heal up" during those rounds of reprieve.
But, IMO, this is a feature of such monsters that is
supposed to make them scary and difficult to deal with. How does the party stop them from retreating to safety and then re-engaging at full strength again? To my mind, that is part of the challenge the PCs face. Can it be frustrating? Oh, yes, but that is the very point of such features.
Now, should they be
unlimited in use? I guess depends on what you want for the monster. My personal preference would be for creatures to be limited to a maximum full hp restore and then no more until a long rest.
This way, if the PCs are winning but struggling, the monster can disengage and heal up, come back for "round 2" so to say while the PCs are still (relatively) weaker. IF the PCs are winning but not struggling (and still "strong") the monster might disengage simply to "fight another day".