I use a rule where if the entire group declares "Run Away!" in a suitably Pythonesque manner, they get away.Running away suffers from the lack of effective escape mechanic.
Depends on the monster. If the PCs invaded a creature's territory and it was attacking to drive them off -- mission accomplished. If the monsters are intelligent and don't want to die themselves, they too might well let the PCs escape. Some other type would certainly try and hunt them down (but you can do that with other mechanics, not staying in initiative).Seems like a cop-out to just drop things when the players all yell, "Run away".
"You all manage to flee to safety and the monster just slithers back to its lair." I guess the DM could narrate some of the fleeing or have the players roleplay some of the escape.
I LOVE it when that happens. So satisfying as a GM.But something about the description of this giant, talking wolf (who literally only cast illusion spells during the combat) and the archers and witches turning into wolves terrified the players, and they spent the whole adventure fleeing from clearing to clearing with the old tortle in tow! It made for a super memorable and fun adventure, and the Wolf King became an ongoing NPC in the campaign.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.