Act 3: How to get into Arena Catacombs?

[bugfragged]

I need that place both for the Lore check and the Black Residue sidequest, but the arena receptionist refuses to give me a quest, even though I cleared the arena in Act 2.

Edit: Nvm, turns out it's actually the second optional quest in Kariid that unlocks it.

Edit 2: Are there consequences for keeping the Ancient Sigil?

Edit 3: Nvm, turns out I can give it to the client, and then use Speech or spend 10000 k to get it back.