The earth rune seems more likely. It's uncertain if he's even capable of duplicating chains.

And unfortunately, without his power glove Jeremy is indeed a bigger danger to us than to the monster, in case he explodes. There has to be some way to put him to use...

And wow Joe, your character did a lot of stuff in a very small time frame. At least i imagine the time between us entering and the monster reaching us to be only a few seconds. Though Important Nobody will have to judge that.
And since you can fire your crossbow several times in a row, i wonder, is it a repeater crossbow or is it just light enough to be pulled back so quickly?

Edit: Oh and i was actually planning to drag Jeremy out of the way if he doesn't post before me, so it's funny that we had to same idea. It's getting late though, so i think i'll post tomorrow.