Play "The Battle of Azanulbizar", which is the second part of "Azog the Defiler", in Free Play mode. Progress until a troll drags in the second tower. Defeat the troll, however do not break the broken section on the tower. An endless amount of enemies will spawn, allowing lots of time to use every dwarf in a Buddy-Up attack. Note: The easiest way to complete this is to use a static player as player two while rotating the dwarves as player one. Consider setting regular Thorin as player two, since his name is last in alphabetical order. Then rotate in Bifur, Bofur, Bombur, Dori, Dwalin, Fili, Kili, Gloin, Nori, Oin, and Ori (all regular/current age) as player one. Each dwarf is conveniently next to each other at the "Character Select" menu. End by using Thorin (Lake-town) with the regular Thorin to complete the task. Note: Make sure you get a complete kill with each combo before moving onto the next character. It also helps having the Invincibility red brick active, to avoid getting killed while rotating characters.