Overlord

The blue hive is found in Heaven's Peak but the cave you have to enter to get to it is surrounded by a green mist from some poisonous plants. There is no other way into the cave so you must get the green hive before you can collect this one.

You get the green hive from Evernight Forest (Viridian Caverns in particular) by destroying all the root endings, the little bulb-like bits and thus gaining access to the caverns.

Once you have acquired the green hive from this area go back to Heaven's Peak and use the green minions to destroy the poisonous plants and get to the blue minions. You need to then work your way through the cave to the hive by following the blue minions. The cave is full of annoying wisp things that mesmerise all your minions apart from the blues so be careful but do kill them to pick up blue lifeforce as you need it to carry the hive.On the way back with the hive, you will encounter a few problems. Twice you will come across these dodo sort of birds. I killed them by getting a blue to grab one of their eggs and lure them towards your other minions. The other enemy is a serpent. You need to lure it into attacking and when its head is down send your minions on to the head. Make sure to call them back after 3 or 4 seconds otherwise you will lose them. Remember that your blues can revive other minions. You should be able to work your way back fairly easily with just these groups of enemies and a few wheels to turn.

Hope that this helps you to get the hive and if you have any problems, please feel free to PM me for any extra help.