Dungeon Hub

The Dungeon Hub gathers everything for The Catacombs and Kuudra in one place: you queue for runs here and use the dungeon shops.¹ You get in through a portal in the Hub's Village; after your first visit it's also on Fast Travel.¹ All damage, fall damage included, is off on this island.¹

Who does what

Mort queues you into the Catacombs through the Party Finder. After Floor III, handing him Saul's Recommendation lets you enter without a party.¹
Malik upgrades items with Essence, dungeonizes gear, reforges and salvages.¹
Ophelia sells dungeon gear and supplies.¹
Crag takes you to Kuudra, and Vulcan runs the Crimson Essence shop.¹
Croesus opens reward chests you didn't claim, from dungeon runs and Kuudra, for up to 72 hours.¹

Races. Guildford runs races below the main area. There are three routes, each with four rule sets (from "anything goes" down to "no items or abilities at all"), and each can be run with or without the way back: 24 races in all.¹ Finishing in time pays Wither Essence, and clearing every objective of a category on a route upgrades the Cat Talisman step by step to the Lynx and then the Cheetah Talisman.¹