Find the Blue Hive - Overlord 2
Follow the straightforward path to reach the palace's magic room and trigger a cutscene. After the cutscene, smash the blue containers to free the Blue Minions inside. Use four of the Minions to turn the wheel nearby and smash the crates to find some health potions.
Sweep your Blues through the Legionaries to turn the wheel at the east end of the room. When the wheel has been turned, some slaves will be released from the nearby cage. The peasants will attack the Legionaries; just stand by and watch the brawl, and kill any Legionaries that survive.
Once you have freed all 15 Blue Minions, head up the steps at the north end of the room to enter the arena.
Quest: Survive the Arena Games
The Arena Games consists of five rounds: a slave round, a Unicorn round, a Gargantuan round, an all-out round, and a Yeti round. At the very start, some Legionaries will smash the containers in the middle of the arena and kill the minions inside. Sweep your Blues to the dead Minions when the Legionaries move on to the next set to revive them. Do not engage the Legionaries; just let them take position by the doors at the other end of the arena. They'll only attack if you get too close, so keep your distance for the duration of the event.
Sweep your Blues in to revive the dead Minions.
Task: Survive the slave round
The slaves are very weak, so this is a simple task. Rather than eliminating all of the slaves immediately, you can walk around the sides of the arena and destroy the containers to release more Minions. To get to the containers on the platform, stand directly below the explosive barrels and hit them once. When the barrels explode, the door at the top of the steps will be blasted open.
Once you have strengthened your horde, take to attacking the slaves. They are very weak, so a swing or two should be enough.
Task: Survive the Unicorn round
This round, you're facing two Unicorns. Unicorns are deadly to both you and your Minions; their charge attack is the biggest threat, as it can kill several Minions at once. It is quite likely that you will lose some Minions this round, however it seems that all of the Minions available during the Arena Games are newborns, so unless you were low on Lifeforce Orbs to begin with, you aren't likely to lose any of your veterans.
The best way to bring down a Unicorn is to wait until it is charging toward you, and then sweep your Minions out of the way and follow them. Then, immediately turn around and begin attacking the Unicorn. If your Destruction tyranny rating is high and you have upgraded the Target spell with Spell Catalysts, you can likely drain a Unicorn's health quite quickly with the spell. Don't approach a Unicorn while it is rearing back, as it can damage you this way too.
Task: Survive the Gargantuan round
Stand behind one of the columns in the middle of the arena and sweep your Minions to the Gargantuan to get his attention. Then, call your Minions back, wait for the Gargantuan to charge into the column, and attack while he is stunned. Repeat as many times as needed to kill him.
Attack the Gargantuan while he is stunned.
Task: Survive the all-out round
You're up against two Unicorns and one Gargantuan in the all-out round. Things are a bit more hectic, but since you made it through the previous two rounds, surviving here shouldn't be overly difficult. It would be best to take out the two Unicorns first, as you can then focus on stunning the Gargantuan. If there aren't any columns standing, the walls of the arena might work as well.
Task: Survive the Yeti round
The Yeti will continuously throw explosive barrels your way. You can't reach him on the platform, but you can use him another way. At the start of the round, turn around and approach one of the double-doors with two Legionaries standing in front. Don't get too close to the Legionaries, as they will attack both you and your Minions. The goal here is to get the Yeti to throw an explosive barrel at the double-door to blow it up.
Stand a few feet from the Legionaries and spin the camera to face the Yeti. When the Yeti throws an explosive barrel your way, sweep your Minions away and follow them to avoid the blast. If the barrel did destroy the door, immediately sweep your Minions through the doorway and follow them up the stairs. If not, stand a bit closer and try again.
At the top of the stairs, step out into the audience and push your way through to the columns holding up the Imperial Lodge. Smash the containers in the stands, and sweep your Minions through the gap to destroy the columns.
When the first two columns have been destroyed, return to the arena and have the Yeti destroy the second double-door. Then, make your way up to the stands and destroy the columns on the other side of the Imperial Lodge to bring it down.
Task: Retrieve the Blue Hive
After the cutscene, you can subdue the Yeti with the Target spell, or kill him. First, move back down to the Arena, collect the copious amount of Gold before it disappears, and take out the Legionaries.
Killing the Yeti will increase your Destruction tyranny rating, and subduing him will increase your Domination tyranny rating. To subdue the Yeti, lock onto him and hold the X/Square button until he shrinks down to size. To kill the Yeti, simply lock-on and overcharge the Target spell once he has shrunk.
Send 10 of your Minions up the ramp to pick up the Blue Hive and they will automatically carry it over to the nearby Waypoint Gate. Now that you have the Blue Minion Hive, there are treasures in previous regions that are now attainable. Refer to the Dark Crystal Locations, Health Upgrade Locations, and Spell Catalyst Locations sections of this guide and pursue the treasures that have “Blue Minions” listed as a requirement.