Psaro the Manslayer is the central antagonist in Dragon Quest IV and a recurring monster in the series. He is a powerful demon with a passionate hatred for humanity.
Psaro hates and is in turn reviled by humans, but revered by demons and the inhabitants of Rosehill. When Rose, his lover, was attacked by humans for the ruby tears she sheds as an elf, he protected her by concealing her in a small fortress he built far away from human settlements. The town of Rosehill grew up around it as others looking for shelter from humans relocated there. Psaro paid frequent visits to Rosehill in order to see Rose. He shares with her his plans to destroy humanity, while disregarding her pleas to stop and pursue peaceful co-existence.
Near the end of the events of Dragon Quest IV, Aamon has Rose murdered, causing Psaro to go insane. He loses what little inhibition Rose had given him and uses the Secret of Evolution to transform into a monster, destroying his mind in the process. The only thing he remembers is his desire to genocide humanity. This leads to the final confrontation between he and the Hero in the Nadiria
Battle
Psaro the Manslayer is fought at the very end of Dragon Quest IV. He is notably the first transforming final boss in the Dragon Quest series, and the electronic medium as a whole. The battle is a test of endurance more than anything, as Psaro's only tricks are ones used by other bosses earlier on, so the player should already be familiar with the methods of dealing with them. He has seven different forms, effectively undergoing an elaborate metamorphosis:
”スクルトで守りを高めドルモーアを使ってくる。弱点の氷の攻撃でこちらのペースに持ち込め。愛するものを殺した人間に復習するため、進化の秘密に手をそめた悲劇のプリンス。” - Dragon Quest IX Beastiary (Japanese)
Psaro appears as a Legacy Boss. He has no current memory of himself, and he challenges the Hero. His map can be dropped from the Dragonlord at higher levels (and thus can be obtained multiple times).
Psaro appears in his final form as a rank X member of the material family and can be obtained by synthesizing a Ruin and Roseguardin together. His Manslayer title is reflected in his default nicknames, all of which contain 'slay'.
The green Goliath form appears as a part of Psaro's Coup de Grace
Trivia
There are two Psaros in the remake; the other one is a gender-confused naked man.
There is an writing error in the IX's Japanese version of the bestiary; it was written 秘密 (Himitsu) when it should have been 秘法 (Hibou, meaning secret act literary.), although it is the same meaning.
Gallery
Dragon Quest Monsters
Dragon Quest Monsters 2
DQM I+II
Dragon Quest Monsters: Joker
Dragon Quest Monsters: Joker 2
Dragon Quest Heroes
Psaro the Manslayer from the Sofubi Monster merchandise series.
Special metallic version in the Sofubi Monster series.