I employed this in a game where the scenario had the party members in a crowded temple – every square occupied by something or something – when the thatch roof caught fire. As good characters the party could not simply hack its way through the peasants and commoners and escaping the mob proved to be one of the most interesting challenges of that game session. The attacking zombie, which had caused he fire in the first place, were almost incidental to “not being stomped to death by commoners.”
Anyway, dealing with a mob in this manner was not something I had experienced an RPG before.
A mob of panicked or angered humanoids functions like a challenging terrain. It prevents movement, inhibits line of sight and potentially damages any creature in the mob. It is not possible to take 10 in a mob.
Moving through a mob requires a successful Acrobatics or Athletics skill check, starting at DC appropriate to the party (Refer to the Skill Check Difficulty Class table under Encounter Settings in the Dungeon Master’s Guide) but increasing by +1 for every turn they are in the mob. Success means the PC moves through the mob as though it were difficult terrain. Failure means the PCs are unable to move. Further, every round they are in the mob requires a STR or DEX (whichever score is higher, depending on the character) check against the DC of the mob. Success means they remain standing, failure means the actions of the mob knock the character prone. Anyone who fails under the crowd is dazed for the remainder of that turn and remains prone until they can stand. Standing requires an Acrobatics or Athletics skill check against the mob’s DC + 10. Anyone in a mob, standing or prone, potentially takes damage – checked against the character’s AC – for every turn the character remains in the mob.
Situation and Potential Damage
Standing or Moving 1d4+1
Being Knocked Down 1d8+1
Note: If the mob is capable of making additional attacks of any kind, it may do so at any time at the discretion of the GM.