Sara is phase 1 of Yogg-Saron. When the round begins, Sara enters play with three Guardians of Yogg-Saron. If more than two guardians of Yogg Saron are in her party, Sara is invincible, however she can attack. Sara cannot be dealt direct raid damage. Instead, the keepers must deal damage to her. I have not yet revealed what each keeper does, but they are on the raider's side and there will be four of them.
At the beginning of each boss player's turn, a die is rolled. If an odd number is rolled, an additional Guardians of Yogg-Saron is put into play. To decide which power Sara will activate, another die is rolled. this uses the chain. Either Sara's Fervor, Sara's Blessing or Sara's Anger will activate. All of these abilities except Sara's Blessing spawn tokens that can be treated like ongoing abilities, and they buff any Guardians of Yogg-Saron in her party.
When Sara takes fatal damage from keeper damage, the fight transitions to phase 2. Immediately, the phase 1 boss is put aside and the phase 2 boss is put into play. Any remaining allies stay in play. This is the most intensive part of the entire fight.
Phase 2: The Mind's Eye and Tentacle Pr0n
Phase 2 has a LOT, and I mean a LOT of crap going on. First, at the beginning of the boss player's turn, one player will choose to enter the Mind's Eye. If someone is already in there, and a new player wants in, the old one will be ejected unless their hero is mind controlled. This works a lot like Black Temple's Teron Gorefiend fight: the player in the Mind's Eye can only attack or effect cards in the Mind's Eye, and player's/characters on the outside (including allies like Sara) cannot affect characters inside the Mind's Eye.
When the phase starts, Sara is relagated to a [2/10] ally with protector who hovers over Yogg Saron; and assists in protecting the tentacles. "Outside" characters cannot deal fatal damage to Yogg Saron's Brain. Phase 2 ends when fatal damage is dealt to Yogg Saron's brain. Additionally, at the beginning of the boss player's turn, an influence tentacle is put into play on the Mind's Eye side of the field.
Yogg-Saron was known for making people mad. Madness is an innate ability that comes into play at the beginning of phase 2and cannot be touched, targeted or manipulated. At the start of every player's turn, they roll a die. If it rolls odd, they put an insanity counter on every raiding character they have. If they gain insanity counters equal to their health value, they go insane and are mind controlled by the boss (the boss takes possession of them) until that player's next turn. The change in ownership removes all insanity tokens.
During Phase 2, anyone outside is dealing with Sara and the tentacles/adds while the player inside the Mind's Eye deals damage to the brain and deals with the tentacles. At the beginning of the boss player's turn, a die
is rolled to determine which power is activated inside the Mind's Eye. This occurs after the effect of staying/entering the Mind's Eye. If the same player wants to stay in the Mind's Eye, they stay inside.
Phase 3: The Head of the Beast
If any influence tentacles were left in the Mind's Eye, they are destroyed and a random outside tentacle is put into play (a constrictor, crusher or corrupter tentacle). The Mind's Eye mechanic ceases to exist, and upon destruction of phase #2 the player inside the Mind's Eye returns outside. From there it is a straight DPS race to kill Yogg-Saron. On turn 6, it is all over. [Extinguish All Life] cannot be interrupted.