I logged in with a Dungeon client, but found myself inside the TriadCity world. What's up with that?
When you log out, your location in the universe is saved. When you return, that's where you'll be — regardless which client you use.
To some degree the clients are interchangeable this way. Entering commands and reading responses is the same with all of them. But, the GUIs are optimized for their particular world. With the TriadCity client for example your Midgaard mana points aren't displayed on the Health tab. With the Midgaard client, they are. Your TriadCity client, meanwhile, knows about Reward Points, while the others don't.
When you create a new character, its "origin world" will correspond to the client you used. So, creating a character with the Dungeon client means that character's origin world will be Dungeon. We recommend always using the Dungeon client with that character. That is, use the client that corresponds to each character's origin world. That'll make sure you're displaying the right stuff in the right context.