Climbing is mostly done with Yu'lon, Nefarian and Sinestra, but you can make adjustments per battle.

The boss battle is done using Onyxia, Kazakus, Golem Shaper and Sinestra. Summon taunt golems to absorb incoming attacks, use Onyxia's attack to deal damage to Avalanchan, use Sinestra for healing and to damage the enemy caster (but prioritize healing).