Do these things need to breathe? You can try smoking them out of the cave. If it's out of the cave, then maybe it won't be able to rely on the power source that's powering its healing factor.
I understand the wariness over the Law Compliance concerns, but you should also be careful with Discord's plans going forward with ID. Honestly, it feels like everything on the internet is just getting worse.
You know, they've been bashing his combat potential for a bit now, but thinking back on it, he's a tutorial boss. His purpose was to teach elemental weakness, his being fire. This implies to me that he should be basically impervious to all other damage types than fire, which is honestly kind of...
Sheesh, the guy's a full-blown working adult with a teaching license, and he never left the petty grudges of the delinquent world behind. He's not even man enough to fall in with the yakuza, so all he can do is bully high schoolers. Pathetic.
They had days to prepare, and they didn't bother preparing any defensive lines? No pitfalls, no traps, no spikes...heck, no shield walls. I'd even be fine with some pavises set up to at least control the flow of battle. The goblins seem pretty stupid and weak, so you could absolutely wreak havoc...