Sirius

Sirius is an NPC standing in front of the Dark Auction House in the Wilderness when the Dark Auction begins. He only appears when the dark auction is happening. Which is every 3 skyblock days at midnight.

When right-clicked with less than in your purse, Sirius will alternate between telling you to leave and splashing you with an Invisibility Potion. He is also the auctioneer of the Dark Auction.

The man is very mysterious, as nothing is really known about him.