Where did this deadly lichen come from, and what can I do about it?

Question

I recently went through quite a bit of effort to survive obtaining a key (fire trap in explosive gas room...). After obtaining said key, I was walking though the only hallway back to the vault on the level, and it was full of "deadly lichen" that had not been there earlier.

I would like to get back to the vault - my potion of detect magic indicated that all the items inside the vault have benevolent magical auras. However, but I don't know how to get past this "deadly lichen", nor am I sure what's its effects on me might be.

To test the effects, I used my wand of beckoning to pull a kobold over onto the lichen, and it immediately became "fatally poisoned" and died within a few turns, so I've determined that walking over it seems like a BAD option.

So how can I get past the deadly lichen?

As a bonus, I'm also curious how deadly lichen forms if anyone knows. It was in the key room, so it may just be part of an elaborate key trap, but I haven't seen this before if that's the case, and it seems a little mean for a depth 3 key room.

Answer 1

The deadly lichen is not as poisonous as the beckoned kobold led me to believe. I decided to risk walking over it and it did minimal poison damage to me.

I looted the vault and picked up a staff of firebolt - I can now verify that fire takes care of the lichen quite easily. I'm sure levitation would work as well, as suggested by yx.

As for where the lichen came from, it seems to have come from a potion of creeping death that I tested in the area - it had absolutely nothing to do with the key room.