Multiple Instances of Brown Mold

[Iammars]

So let's say that you have multiple undead creatures covered in brown mold. A fighter is standing next to two of these creatures. Does the brown mold deal 3d6 cold damage or 6d6 cold damage?

[PrinceDogWaterIII]

The character in question would take each hit of 3d6, remember these while happening at the same time apply Cold resist to each 3d6. I would imagine it happens at the beginning of the character's turn. Similar to how the fiery aura ability of Burning Skeletons functions.

[Lincoln Hills]

This is from 3.5 and therefore not "canon," but I recall Paizo's remake of Maure Castle including one area where brown mold was so thick on the walls and floor that their multiple auras intersected. The overlapping cold auras in that area interacted just as PrinceDogWaterIII says they would, above.