Boss 18
Parvin
Zone: Ommog Tower, Floor 1
Boss 19
Villard
Zone: Ommog Tower, Floor 2
Boss 20
Arhkham
Zone: Ommog Tower, Floor 3 Portal Master: Stellar Observatory
Boss 21
Arthas
Zone: Ommog Tower, Floor 4
Boss 22
Talus
Zone: Ommog Tower, Floor 4 Portal Master: Forge of Heaven and Earth
Boss 23
Ripper
Zone: Ommog Tower, Final Floor. Slay Talus and enter the new portal.