Cú Chulainn (Caster) stems from Irish myth as a demigod and Ulster Cycle hero, son of mortal Deichtine and sun deity Lugh. In official narratives, Odin’s intervention radically alters his Lancer-class identity, appointing him a proxy to address threats to the Human Order. Bestowed divine authority during the Fuyuki Singularity, he adopts the Caster class, wielding advanced runic magecraft and tactical wisdom to mentor allies rather than engage directly in combat. Originally summoned as Lancer in Fuyuki, his rebirth as Caster under Odin’s patronage shifts his focus to strategic guidance. Collaborating with Chaldea, he manipulates events through runes, mentors Mash Kyrielight, and dismantles the corrupted Holy Grail system. His Noble Phantasm, *Wicker Man: Cage of Scorching Flames*, merges druidic ritual symbolism with Odin’s wisdom, embodying themes of sacrifice and purification. Reappearing as Grímr the Sage in *Avalon le Fae*, he retains prior summoning memories, operating covertly in the English Lostbelt. Shapeshifting into a white wolf, he safeguards allies like Mash and Habetrot, blending Odin’s foresight with innate heroism. Interactions with Scáthach and Sigurd underscore nuanced tensions between reverence for his mentor and pragmatic independence. *Fate/Grand Carnival* shifts tone, framing him as a comedic foil subjected to exaggerated demises, reinforcing the franchise’s “Cú Chulainn ga shinda” meme. This contrasts his grave roles elsewhere, highlighting narrative versatility. Caster’s abilities emphasize runic offense/defense, evasion, and self-sustenance via skills like *Disengage*, which removes debuffs and heals. Post-Lostbelt enhancements amplify his Noble Phantasm with delayed buffs and sacrificial mechanics, mirroring themes of cyclical rebirth. Though tactically adept, his reliance on teamwork cements his role as a collaborative strategist. His arc weaves divine responsibility with tragicomic misfortune, balancing mythic weight against self-aware levity to solidify his layered presence across the franchise.