Unlike other villains in the show, Toffee is incredibly intelligent and manipulative, playing Ludo and his army as pawns in his ultimate goal. He is immortal and has high regenerative powers. He fought against Queen Butterfly years ago when she used her strongest magic to sever his finger which he was unable to regenerate as the spell is meant to kill immortals. This magic was taught to her by Eclipsa, a queen that married a monster and became known as the Queen of Darkness. In exchange for learning the spell, Eclipsa would eventually be freed upon Toffee's death. Toffee is also responsible for killing Queen Butterfly's mother who was making a peace treaty to benefit Mewmans and monsters.
In the first season finale, he forces Star to destroy her wand in order to save Marco. When the wand self-destructs, he merely grins as he is caught in the explosion. The explosion seemingly destroys his body, but his evil spirit inhabits the fractured right crystal in Star's wand which is found by Ludo.
However, it is later revealed in the third season that he was not destroyed, but was transported into the wand entirely. When Star realizes this, she uses the whispering spell to enter the wand herself to confront Toffee, who was absorbing magic. Toffee gains the upper hand and regains his finger. However, Star is able to purify the wand of corruption and uses immense magic to take on a new form that sears Toffee's flesh leaving goop and bones behind. Toffee survives and claims all his actions have been planned, but Ludo knocks a pillar down on what's left of Toffee, seemingly killing the monster for good. While it remains a mystery whether or not Toffee really is dead due to his immortality, it's shown that Eclipsa's crystal prison has begun to crack, hinting that Toffee really is dead.