You start the fight by talking to Finkle in his cage, starting up the Bile-O-Tron. As long as the Bile-O-Tron is active, no one in the raid whose hit points are above 10,000 will die. Any killing blows on a raid member with at least 10k hit points will merely take them down to 1 hit point. At that point, a healer can quickly get them back above 10k hit points. At no point should healers be struggling to get raid members above 10k, except for tanks. This is a test of reaction speed, not raw healing power.
Phase 1 Your raid should stay split up and scattered, due to Caustic Slime. This ability hits four players at a time and does damage to anyone within 6 yards of the player; additionally, the player will have a hit debuff for a brief time. Because you're protected by the Bile-O-Tron, you will not die when hit with this. You only want one player to get hit (thus, you spread out) so that the healers only have to heal one person for each slime.
You'll need two boss tanks for this encounter, both to swap the boss after the use of Break in phase 1 and because there is no healing in phase 2. Chimaeron will hit the current tank hard with Double Attack. This is two hits in quick succession. That means even if your tank is over 10k HP -- and thus reduced to 1HP on the first hit -- he will not have that protection on the second attack. Chimaeron also hits the tanks with Break, which stacks a healing debuff. This means you need your tanks to trade off and swap Chimaeron after a few Breaks so that it doesn't become unmanageable. Tanks will want to manage cooldowns carefully to help survive this damage during the second Break.
Massacre instantly deals millions of unmitigated points of damage to the entire raid. Everyone above 10k hit points will instantly drop to 1 HP, and anyone under 10k HP will die. This includes the tanks, so healers should be ready to top them off immediately. When Massacre hits, the Bile-O-Tron will briefly go offline, starting phase 2.
Chimaeron will follow up with another Mortality to take you back into phase 1.
Phase 3 At 20%, Chimaeron enters phase 3. Chimaeron hits the entire raid with Mortality, making healing nigh useless. He also becomes untauntable. On the bright side, he takes an additional 10% damage in phase 3.
At this point, burn every offensive cooldown you have and get him down as quickly as possible. Kite him, bubble, trap, and snare with everything you have. This is simply where your DPS must shine.
- Tankspot's guide to Chimaeron
- Wowpedia's page on the boss
- Wowhead loot list and information
- Yogscast guide to Chimaeron
Ready Check shares all the strategies and inside information you need to take your raiding to the next level. You might also be interested in our strategy guides to Cataclysm's 5-man instances, and for more healer-centric raiding advice, visit Raid Rx.