Helm Splitter and Skull Splitter

Helm Splitter and Skull Splitter are both Venus class Psynergies in the Golden Sun series, although Skull Splitter was not introduced until Golden Sun: The Lost Age. They are only availile to the Samurai and Ronin classes at level 33. Helm Splitter is available at the Samurai class, but upon reaching the Ronin class Helm Splitter is removed from the Adept's available Psynergies when Skull Splitter is added; in other words, Skull Splitter effectively replaces Helm Splitter. Being available to only these two classes, only Isaac, Felix, Garet, and Jenna have access to them.

Helm Splitter
Helm Splitter: "Paralyze a foe with a mighty blow." Helm Splitter costs 8 Psynergy Points to cast, targets one enemy, and does damage equal to the base attack plus 30.

Skull Splitter
Skull Splitter: "Annihilate a foe by crushing the skull." Unlike most Psynergy pairings of similar nature, Skull Splitter has the exact same stats as Helm Splitter, meaning it costs 8 Psynergy Points to cast, targets one enemy, and does damage equal to the base attack plus 30. The difference is that it has a chance to immediately down a foe.