The Chaos Sanctuary is the lair of Diablo himself and the final location in Act 4. Players who seek to destroy Diablo must enter his Sanctuary and open all five seals in order to clear their way to the final battle.
Three of the five seals release a super unique monster with a group of boosted minions. These are:
Once all seals are opened and all super uniques dead, Diablo will be summoned at the central pentagram. On Destruction difficulty, killing each super unique will cause swirlies to appear around the players, allowing them to use the oskill Dark Portal and open a portal to an uberlevel depending on the super unique: