Gollux

I think the thing that makes the least sense is the keys though. Like, you buy your 5 keys and then if you somehow don't have enough drop in those 5 fights to go in and keep getting more or if you drop all your keys you suddenly can't fight gollux at all, never again. I mean i know the keys have a good drop rate, enough to make a gain of keys if you kill enough monsters with the right drop rate, but it is possible. Do they really want people to be blocked off from their newest content?

Try talking to that NPC on a Yak. She has a daily quest that gives up to 3 keys daily for free. You have to be in her map, I mean, it's not like Root Abyss keys. I just redid the quest today, so I'm fairly sure it's repeatable every day or at least every so often.

Apparently, it's mostly to re-enter without actually killing Gollux to farm coins and more keys to re-enter. It's weird to have it like that, yes, but that's the way they thought.