Cu Chulainn (クー・フーリン, Kuu Fuurin) is a recurring demon in the Shin Megami Tensei series. He is associated with Setanta, which the Protagonists must often train Setanta to a sufficient high level before obtaining Cu Chulainn. In the Persona series, Cu Chulainn appears as a mid-level Persona, available to summon once the Protagonist reaches a sufficient high-level.
"A legendary hero in the Celtic folklore. His name means the 'Hound of Culainn' and his true name is Setanta. There are many tales of his exciting adventures with his spear Gae Blog."
Cu Chulainn is an Irish mythological hero who appears in the stories of the Ulster Cycle, as well as in Scottish and Manx folklore. The son of the god Lugh and Deichtine, sister of the king of Ulster, he was originally named Setanta, but gained his better-known name as a child after he killed Culann's fierce guard-dog in self-defense, and offered to take its place until a replacement could be reared. At the age of seventeen he defended Ulster single handedly against the armies of queen Medb of Connacht in the epic Tain Bo Cuailnge. It was prophesied that his great deeds would give him everlasting fame, but that his life would be short – one reason he is compared to the Greek hero Achilles. He is known for his terrifying battle frenzy, in which he becomes an unrecognizable monster who knows neither friend nor foe. He fights from his chariot, driven by his loyal charioteer Laeg, and drawn by his horses, Liath Macha and Dub Sainglend.
Cu Chulainn appears as a distinct demon in Shin Megami Tensei III: Nocturne. He cannot be encountered nor recruited by the Hito-Shura, rather, the Hito-Shura can only obtain him by evolving Setanta by reaching at least Lv. 52 himself and completely mastering Setanta's skillset.
Digital Devil Saga: Avatar Tuner
Cu Chulainn appears as a normal enemy encounter in Digital Devil Saga: Avatar Tuner. He can be easily found in Coordinate 136. Cu Chulainn is also one of the Demon allies summoned by the optional boss Hito-Shura during battle; he focuses on lowering the party's Defense and striking them with powerful Physical attacks.
Digital Devil Saga: Avatar Tuner 2
Cu Chulainn returns as a normal enemy encounter in Digital Devil Saga: Avatar Tuner 2. He can be easily found in final dungeon, the Sun. Cu Chulainn often appears alongside with Pallas Athena when fought.
Cu Chulainn appears as the Persona of the Tower Arcana in Persona 3. He is available to be summon once the Protagonist reaches Lv. 40 or above. Cu Chulainn, along with Scathach also grants the Protagonist the Fusion Spell Shadow Hound, which inflicts severe Strike damage upon all enemies.
Persona 3: FES
Cu Chulainn returns as the Persona of the Tower Arcana in Persona 3: FES, retaining all of his attributes. However, as FES introduces the weapon fusion system, Cu Chulainn can be fused with a Nihil Spear into a distinct weapon at the antique shop via the Weapon Fusion system. The weapon is Gae Bolg, a Spear holding 260 ATK, 85 Accuracy, and the passive ability Wind Amp. It should also be noted that Gae Bolg inflicts Wind-based damage upon striking enemies with it, rather than dealing pierce attacks.
Cu Chulainn returns as the Persona of the Tower Arcana. He can be summoned once the Protagonist reaches Lv 46 or above. Cu Chulainn's in-game model is also re-used as another Persona of the Sun Arcana, Tam Lin; Though two Personae shares different attributes and color schemes.