Overview Jaraxxus is significantly more complicated than any of the Northrend Beasts encounters, but is still a relatively easy fight. He will cast Fel Fireball and Fel Lightning, both of which can hit for quite a bit. The former can and should be interrupted every time - if it's not it applies a DoT on its target, which should be dispelled quickly. Fel Lightning is easy to handle if your ranged spreads out well. Couple of spells to check your reflexes - Incinerate Flesh and Legion Flame. Incinerate Flesh will absorb a certain amount of healing on whoever it's cast. If the spell doesn't absorb its maximum amount in the 12-seconds duration, the target will cast a powerful raid-wide AoE. And Legion Flame will spawn fire under its target every second - movement is a key here. Two types of adds will be summoned as well. The Mistresses of Pain come from Nether Portals the eredar summons. These should be offtanked in the middle, next to the boss, to avoid Fel Lightning bouncing to the melee; offtanked and killed quickly, as they will jump to random raid members and hit them hard. The other type of adds are Infernals summoned in groups of 3-4 from Infernal Volcanos, spawned by Jaraxxus. Those have a nasty fire AoE, which can be interrupted. They also have low health and can be stunned, so you should take them out quickly. And lastly, Jaraxxus will buff himself with Nether Power - a buff that starts at 10 stacks and increases his spell damage by a lot. These should be removed as quickly as possible by any means necessary. Abilities - Inflicts 15,113 to 15,887 (25-Players: 24,375 to 25,625) Fire damage and an additional 5,850 to 6,150 (25-Players: 9,263 to 9,737) Fire damage every 1 second for 5 seconds. The cast can be interrupted, and the DoT is magic effect. - Inflicts 7,863 to 9,137 (25-Players: 9,713 to 11,287) Fire damage to a random target and jumps to other players nearby, affecting up to 3 (25-Players: 5) targets. - Absorbs the next 30,000 (25-Players: 60,000) healing done to the target and reduces damage done by 50%. If the spell is not removed by healing, it will cause Burning Inferno. Lasts 12 seconds or until the spell absorbs its healing limit. - Inflicts 2,438 to 2,562 (25-Players: 3,900 to 4,100) Fire damage every 1 second for 5 seconds to all friendly targets. Cast by the target of Incinerate Flesh if the latter is not removed before its duration expires. Incinerate Flesh is removed after absorbing 30,000 (25-Players: 60,000) healing. - Inflicts 2,925 to 3,075 Fire damage every 1 second for 6 seconds. The target also spawns a Legion Flame every 1 second. Each Legion Flame inflicts another 2,925 to 3,075 Fire damage every 1 second and lasts for 60 seconds. - Summons an Infernal Volcano, which shoots 3 Felflame Infernals at players over 15 seconds. Every time an Infernal lands, it causes Infernal Eruption, inflicting 9,263 to 9,737 Fire damage to targets in a 10 yard radius. Felflame Infernal - Can channel Fel Inferno to inflict 2,500 Fire damage every 1 second for 6 seconds to targets within 15 yards. Can use Fel Streak to charge a target, inflicting 4,388 to 4,612 (25-Players: 6,338 to 6,662) Fire damage to any target on its path. - Summons a Nether Portal and inflicts 6,825 to 7,175 (25-Players: 9,263 to 9,737) Shadow damage to targets in a 10 yard radius of the portal. The Portal spawns a Mistress of Pain. Mistress of Pain - Uses Shivan Slash, inflicting 50% weapon damage and ignoring armor. Can also cast Spinning Pain Spike on a random target, inflicting high physical damage based on the target's maximum health. - Increases magic damage done by 20% per application. Jaraxxus will buff himself with 5 (25-Players: 10) stacks. Trial of the Grand Crusader For details about the specific differences in this fight on Heroic difficulty, check this blog.