The Trollmire is a first-tier dungeon in the northern part of Maj'Eyal, near Derth. It has a material level range of 1 to 2 (or 3 to 4 after returning from the Far East). The Trollmire is the starting zone for any race/class combination that doesn't have its own special starting zone.
The Trollmire is inhabited mostly by trolls and animals. It uses a dense forest layout, mostly trees with highly irregular, short, random paths and some clearings. Since beta 32, there is a road connecting the exits and leading to the boss's clearing.
The official boss is Prox the Mighty, a troll; but Prox's boss is Bill (also a troll, and substantially tougher), whose treasure-filled dwelling is on the secret fourth level. (If you started in the Trollmire, and have only beaten Prox, you are probably level 4-5 and should postpone your chat with Bill, unless you want a seriously challenging fight.)
If you are playing the "alternate" Trollmire (which you can tell by a high level of water), the boss will be Shax the Slimy.
The Trollmire can have 6 kinds of vaults: honey glade, ruined building 1 through 3, snake pit, and mage hideout.
The Trollmire is one of the easiest dungeons in the game as it has a very reduced chance of rares spawning (along with Kor'Pul) and low tier monsters. Besides trolls and wolves which only do physical attacks you can encounter some plants and snakes, which can poison or bleed.
A unique Troll Hedge-Wizard may spawn in any of the levels (including Bill's Lair). He is a spellcaster and has access to the powerful Rune of Reflection which shields and reflects all damage he receives. As long as you avoid attacking him while he has his shield on, you'll be fine. Upon killing Troll Hedge-Wizard, he drops Rune of Reflection for your own use.
The regular boss (Prox the Mighty) isn't very dangerous. Unless he rolls a troubling class (can only happen on Insane difficulty) he will not pose any kind of threat.
In the 4th floor Bill awaits. He will hit you significantly harder than Prox on top of having access to advanced talents. When he first comes into vision he's likely to try and Rush to you and stun/daze you, so activate a movement infusion immediately. As long as you're paying attention and using your abilities correctly he will be very easy.
There is an achievement you can obtain here. If you attack Prox at level 1 and lower his health until he drops a paper but don't kill him, you'll unlock Hidden Treasure. If you can manage to get to Bill's Lair and kill him with Level 1 you get the Kill Bill! achievement.