A friendly skirmish produces a great reward.

Thane, the gigantic, bearded trainer at The Forge, teaches Death new attacks, and always wants to spar. If you best him in battle, he reveals the location of four beasts as four separate side quests.

Although you can challenge Thane early in the game, you stand little chance against him. Quest for a few hours, and return to him when you reach level four or five. Your weapons deal plenty of damage at this point. The battle ends if Thane hits you a few times. Don't go right at him. Wait for him to attack, and then dodge and counter. Repeat this process until you drain three-quarters of his life. At this point, he'll end the fight and fill you in on the four beasts. Your targets are Bheithir, Gorewood, The Deposed King, and Achidna. Each of these bosses drops a unique weapon.

As readers are pointing out, you may run into these beasts prior to defeating Thane. However, with Thane's help, the location of each beast appears on the map and can be made an active quest. To do this, go into the map screen and access the Toggle Quest Display menu to choose your quest. Since these bosses are high in level, most of them don't appear on the first map. Just make a mental note to check your quests whenever you reach a new zone.

Apologies for the iPhone 3GS photo. I don't have video recording equipment in my house.