Realm of the Rat is the first dungeon most players will attempt. It takes place in a tunnel system made by giant rats, who are predictably unhappy about you being in their home. It is a five player dungeon with a ten player hard mode, and if your party has less than five or ten members when entering, NPCs within the level range of the current members of the party will join you in the dungeon.
The first thing you will notice when entering this dungeon is that unlike the tutorial and parts of the overworld, all attackable NPCs in this dungeon are aggressive; they will attack without being provoked. The larger rats (not the unattackable baby rats) are elites, which means they are significantly stronger than most enemies their level and will require teamwork to defeat.
After you make your way through the entry area, you will encounter the first of three bosses: Rattington. Rattington has attacks unlike those of the enemies you will have encountered so far; he can burrow underground to avoid damage, burst out of the ground for high damage, and eat the nearby roots to restore health. The roots regenerate, but can be destroyed by attacking them, preventing Rattington from regenerating health.
After Rattington, the next boss is Ratina, Queen of the Rats. First, however, you will have to make it past more of the elite rats, either by force or by stealth.
Ratina, Queen of the Rats has a completely different style of attack than Rattington. Where Rattington attacked on his own, Ratina attacks by sending her servants to do it for her. She can call warriors, who have even more power than the elite rats; tunnelers, who can burrow underground and burst out in a different location, similarly to Rattington; or guards, who can hold a player with their tail and prevent movement or attacking.
Although Ratina cannot be damaged, attacking her will buy you more time before she calls the next set of servants. Ratina will call a total of ten servants in groups of two.
Ratimilian, King of the Rats is the final boss. Ratimilian has the ability to burrow underground, set deadly spike traps, and then burst out of the ground, triggering all the spike traps at the same time. He can also damage players directly in front of him with a fierce bite, and knock down players behind him with a tail sweep. His “chosen one” attack causes his current target to be the only healable player for thirty seconds, so it is important that the tank knows this encounter well.
Rewards from this dungeon range from daggers and stolen jewelry to earth-coated robes and armor. The special ability of trinkets from Realm of the Rat is “burrow underground, becoming immune to damage but unable to attack or cast spells for ten seconds.”