I Choose You, Steelbreaker (10 player)

Kill Runemaster first, then Stormcaller, and finally Steelbreaker. Each boss killed supercharges the remaining bosses, healing them to full and granting new abilities, so saving Steelbreaker for last is what triggers the hard mode conditions required for this achievement.

Run with either 2 tanks, 2 healers, and 6 DPS or 2 tanks, 3 healers, and 5 DPS depending on your group's capability. Avoid bringing 3 tanks, as this is not recommended for this encounter.

A Paladin tank on Steelbreaker is strongly advised because Paladins can dispel Fusion Punch from themselves easily, and dispelling the Steelbreaker tank is a hard requirement throughout the fight.

A Hunter using Aspect of the Wild or a Shaman dropping a Nature Resistance Totem will reduce damage taken from Steelbreaker's High Voltage and Fusion Punch abilities across the raid.

Bringing a Shadow Priest for Vampiric Embrace or a Retribution Paladin for Judgement of Light significantly helps sustain the raid through Steelbreaker's constant AoE damage from High Voltage.

While Runemaster is being killed, have players taunt Stormcaller to prevent him from chasing healers, and interrupt his casts as frequently as possible. Once Runemaster dies, everyone should focus interrupts and stuns on Stormcaller immediately.

After both other bosses are dead, Steelbreaker debuffs his primary tank with Overwhelming Power, doubling that player's damage dealt but causing a fatal Meltdown explosion after one minute. Use tank switches and cooldown rotations to manage this debuff, as each player killed by Meltdown grants Steelbreaker a stacking 25% damage increase.