Conjoined Twins

The "boss" actually comes in the form of multiple mobs which share an HP pool, resurrect if only one of them is killed, or something similar. In practice, the DPS usually splits up somehow to handle these encounters. If the bosses are tackled in sequence, or are otherwise relatively unique entities, you are probably in a Multiboss encounter.

Examples

• Molten Core
  • The Core Hound packs will respawn themselves if all hounds aren't killed within a few seconds of each other.
• Temple of Ahn'Qiraj
  • The Twin Emperors.
• Naxxramas
  • The sub-bosses before Thaddius must be killed together.
• Ulduar
  • XT-002 Deconstructor's Evocation Phase exposes a heart which can be DPSed, and whose damage is then shared with the boss himself.
  • Kologarn's Left and Right Arms can be independently targeted and brought down; killing the Right Arm in particular is an integral part of the strategy.
  • One type of summoned add that Freya uses is a trio of mobs (who don't have equal amounts of HP) that must all be killed together.
• Trial of the Crusader
  • The Twin Val'kyr share an HP pool.