Ultra Death

Ultra Death is a boss added in The Binding of Isaac: Repentance and is the last of the Ultra Harbingers fought before The Beast in.

Behavior
Unlike the other Ultra Harbingers, Ultra Death has only one phase and has three attacks which it cycles through indefinitely:
 * Summons a rectangle of 11 Ultra Death Scythes which close in towards Ultra Death's position and continue in the same direction until disappearing off screen. Ultra Death uses this attack 3 times in a succession.
 * Flies off screen, then reappears travelling slowly while summoning waves of Ultra Death Heads which move up and down across the screen in the same direction. At the end of the attack, the skulls freeze in place and Ultra Death summons three harmless scythes which spin outwards, destroying the skulls.
 * Immediately after the previous attack, the screen darkens and Ultra Death disappears into the darkness. Ultra Death appears next to Isaac and swings its Scythe before disappearing again, darkening the screen with each attack. This attack is repeated 4 times, afterwards, the screen returns to normal and Ultra Death reappears.
 * Its position during this attack can be indicated by a faint glowing red eye.

Trivia

 * Ultra Death, like the other Ultra Harbingers is an upgraded version of its regular counterpart, Death.
 * Unlike the others, it has the greatest variation in behavior from regular Death- notably the lack of a second phase.
 * The violin heard in the section of Revelations 13:1 that plays during Ultra Death's fight is performed by Carla Kilhstedt, the voice actor for Mom.
 * Ultra Death can be seen facepalming in the background after killing Ultra War.
 * The wave of Ultra Death Heads loosely resembles one of Conquest's attack.
 * This could be compensation for Conquest's lack of appearance despite his Harbinger role.
 * Ultra Death's glowing eye during the darkness attack could be a reference to the Terminator series, as Ultra Death bears some resemblance to the Terminators seen in those movies.