Breather Boss / World of Warcraft

• Rather than fighting a certain boss normally, you play Chess with him (not the real chess, it has its own rules). Despite the fact that the boss cheats, it's not hard to win it, but it's certainly a different experience.
• Noth the Plaguebringer. He's a fairly easy boss, but, apart from some easily-downed trash, he comes immediately before the dreaded Heigan. Get your dancing shoes on.
• Ulduar: First, there's Flame Leviathan, a very innovative encounter using vehicles, but he's a complete pushover. Razorscale is not much harder. Then come XT-002 and Ignis who will eat you alive. Similarily there's Auriaya in central Ulduar, who is not particularily difficult except for the pull, that requires high amounts of coordination, but other than that, the boss is rather easy... and immediately followed by the watchers, who are much harder. And Mimiron WILL make you weep in despair.
• Burning Crusade had the Void Reaver, a slightly beefed up version of the Fel Reavers that run around Hellfire Peninsula and slaughter lower level characters. He was standing in Tempest Keep, where one of the hardest Bosses of all time was found, together with another two fairly difficult encounters... and the Trash before him is effectivly a lot harder than he himself. He could take a beating, but as long as most of the raid pays attention he is ridiculously easy. So easy that it was advised to try him as soon as you could beat a single boss of a lower Tier. They called him "Loot Reaver" for a reason. Void Reaver was inadvertently made a lot harder after he got changed in a patch, though. Originally he was bugged, causing him to shoot his attacks (which you are supposed to run out of the path of) from his feet rather than his head. This was later fixed, which - since he's an insanely tall robot - had the side effect of making these shots impossible to see until they hit you. People had to use scripts to increase the viewing distance beyond the default maximum to work around this.
• In Icecrown Citadel, Lord Marrowgar and Lady Deathwhisper are quite difficult for players who haven't run through the dungeon very often. Then comes the gunship battle, which is easy enough to be nicknamed the "Lootship" battle, as it basically consists of fighting off adds while shooting the enemy ship with the cannons, and occasionally killing a mage who disables your cannons. The Deathbringer, who comes soon afterward, is a relatively simple DPS race if the raid knows how to deal with Mark of the Fallen Champion. Valithria Dreamwalker, whom many raids go to after the more difficult Plagueworks and Crimson Hall bosses, is quite easy compared to others, as it mainly consists of killing adds while healing the dragon. The gunship battle was in fact so easy that groups which had no hope of completing Icecrown Citadel on normal difficulty still regularly beat the gunship battle on heroic difficulty, despite heroic difficulty being otherwise tuned so that the first bosses on heroic are harder than the last boss on normal.
• In Cataclysm, Blackwing Descent begins with the relatively easy Magmaw and the fairly difficult Omnitron Defense System. Then the next boss is Maloriak, who has relatively simple mechanics, and the only difficult part is managing the release of the aberrations so they're all dead before the second phase.
• In the new version of Shadowfang Keep, Baron Silverlaine comes after Baron Ashbury (who is quite difficult for groups who can't interrupt properly), and his only abilities are a healing reduction debuff and summoning adds to be defeated.
• Murozond in End Time. He has a very large amount of HP, but the ability to rewind time (which resets cooldowns and even revives dead players) five times makes killing him easy, especially since you can use Bloodlust/Heroism/Time Warp five times. He also has few abilities, only a breath attack and AOEs that leave behind "fire" on random players.
• In Throne of Thunder, Primordius is this after the fairly difficult Durumu and the complex but manageable Dark Animus. Primordius only has a few abilities, and most of the encounter involves killing slimes to prevent him from "evolving" and gaining a damage buff and a new ability, while then turning your attention to him once you have enough buffs and are mutated. All in all, it's a relatively simple fight. In the last wing, Iron Qon and the Twin Consorts are fairly straightforward lead-ups to the fiendishly complicated Lei Shen fight.
  • In Siege of Orgrimmar, Galakras and the Dark Shaman present two tough fights that require a lot of coordination, luck and manic running around. In between is the Iron Juggernaut, a giant robot scorpion siege engine that can be easily defeated within the time limit and is unlikely to kill anyone as long as the tanks are doing their jobs properly.
• Magmorax in the Aberrus raid in Dragonflight is a substantial difficulty drop compared to previous bosses prior such as Rashok and Zskarn, having comparatively very few mechanics which are all simple to handle. The developers uncharacteristically admitted that Magmorax should have been earlier in the raid to provide a more gradual difficulty curve.