Sprinkling Kinak hints around the wiki from Podcastrophe 34:
"There is some other… effects from that."
Additionally, in response to a question on this + toxic crystal + toxic eyeball (in response to an earlier hint — we've found half of what makes one of these items interesting, apparently):
"I feel like I wasn't referring to the +1 XP <that the angel gives you with serpent venom><…> I think the +1 XP is <cackle> interesting. I don't actually remember answering that question but <I don't think I knew you had found the +1 XP> so I'm betting I was talking about something else."
(Vague man… da da da…)
EDIT:
Podcast 37: the toxic crystal, venomous angel, and toxic octopus eye trio of items. Still trying to figure out what the "half we found" was. Kinak's response this time:
I seem to recall the question had the information buried in it, but that was as you said a LOOOONG while back. The interaction there is mostly with a technique that doesn't come up much, so I guess that'll be your hint.
In the beginning, men were mortal.