Where is he?

Loghaire. He's where Randver says he is, in the Dredge. There's a shortcut available is you're persuasive enough, otherwise enjoy another dungeon crawl.

I can't find him in the dredge though....I went through and can't find him, i found the heirloom train, and killed monster after monster but I can't seem to find a new level of the tunnels or another passage....UGH!!!!!!!!!!!!!!!!!!

Wrong dungeon! The toy train is in the mines. The Dredge is a larger, and nastier, dungeon. The entrance is on Level 2 of the main levels, across the hallway from the mine entrance.

The entrance to the dredge is guarded by a platemail dwarf on the same level as outside the throneroom. They let you in if you have already spoken to Randver and then tell them to let you in. Once you go through the dredge, you eventually get to a room where a lot of the monsters are already dead with furnaces and turned over carts in it, as well as a cave entrance in the back wall. You have to click on the cave entrance to go into Loghaire's hideout.

You can also find "Longhair" much quicker if you speak to his son, the reigning king "Longbeard".