Fire Elementals, Fire form

[Calar_Gaia]

So we have a Moon Druid that just got the Elemental form wild shape. With the creatures "Fire Form" trait, it says "The first time it enters a creature's space on a turn, that creature takes 1d10 fire damage, and catches fire; until someone takes an action to douse the fire, the creature takes 1d10 fire damage at the start of each of its turns."

He has taken a liking to disengaging, and then running through every creatures square, dealing d10 fire damage each time and setting each creature on fire. I know for sure that the "set on fire" damage doesnt stack with itself, but what about the rest? Is this scenario RAW? Dealing automatic 2d10 per creature times however many creatures there are seems strong compared to the other elementals dpr capability.

[hymer]

So we have a Moon Druid that just got the Elemental form wild shape. With the creatures "Fire Form" trait, it says "The first time it enters a creature's space on a turn, that creature takes 1d10 fire damage, and catches fire; until someone takes an action to douse the fire, the creature takes 1d10 fire damage at the start of each of its turns."

He has taken a liking to disengaging, and then running through every creatures square, dealing d10 fire damage each time and setting each creature on fire. I know for sure that the "set on fire" damage doesnt stack with itself, but what about the rest? Is this scenario RAW? Dealing automatic 2d10 per creature times however many creatures there are seems strong compared to the other elementals dpr capability.

It sounds right to me, and exactly the sort of thing I'd expect a player to use that form for. Dealing around 11 fire damage (1d10 on druid's turn, 1d10 on enemy's turn; would be slightly better if it was all in druid's turn) to a group of tightly packed enemies isn't particularly powerful at lvl 10, I should say. Fire is the least reliable damage type except for poison, and the amount is small. Big groups of lesser creatures are there to me mowed down by AoE spells and effects, so let the players have fun with it.

If you really feel this is a problem, you can use fewer, stronger enemies, and/or spread your bad guys out further, so he can't get them all.

[Rhaegar]

Normally moving through another creatures space counts as difficult terrain. It's vague weather or not this would apply to fire elementals or not given some of their other abilities. But if you find it to over powered having them use their full move, giving them difficult terrain moving through the target would limit it's overall power to chain through more than a couple targets.

[lebefrei]

It's both fine and allowed; not a bad strategy, honestly. The thing to keep in mind is that it is limited in use, damage type, and that druids can do similar AoE damage with moonbeam. That isn't including higher level spells like Ice Storm.

If you are keeping to Long Rest and two Short Rests, with 6-8 encounters per day, he can do this in 3 fights total. He is also making himself a big target for every enemy. In a big fight this could be a lot of trouble for him. Spread enemies out more, use archers at the fringes, put water on the map, or use demons and devils.

A druid by level 10 has 3 level 2 spells slots to use on moonbeam, if they so choose. This can be moved 60 feet per round as an action, giving it slightly greater range than his elemental. It does radiant damage, a significantly more useful damage type. They can also use higher spell slots for more damage and more uses.

Long story short, it checks out in limited use comparable to other level 10 options, and is something you can strategize against.