ToME: the Tales of Maj'Eyal

Unconfirmed, but I'm pretty sure that Volcano (from the Fiery Choker) targets randomly within a radius of the player, not itself.

I'm confused, how are those two things different?

Volcano creates a map effect at a location, that then shoots at enemies. The player and the volcano are in different locations.

By this bug do you mean a scenario like this happens?
Volcano is active, surrounded by monsters the player teleports far away next to a single monster, and though the Volcano is supposed to randomly hit the monsters 30+ tiles away, it hits the single monster a space away.

Yes. It can also hit the tile that the player is on (30 tiles away from the volcano).

I also saw the thread about the eel-skin proc, good job on bug hunting, far better than myself.

Apparently when you have half a dozen or so volcanoes up, you can get hit about 10 times in a round, triggering a lightning or two in the mix... Used my Blood of Life on that one.