Serina

Serina is the sassy, bossy and overwhelmingly snarky AI in charge of the Spirit of Fire. Her vast intelligance makes her somewhat big-headed, but this doesn't stop her from working effectively as a tactical control center for the UNSC operations on Arcadia and the Flood-controlled Shield World.

Her efforts effectively co-ordinated the entire marine forces to allow Captain Cutter to concentrate on overseeing Red Team in their efforts to decapitate the Flood leadership and save Ellen Anders from the Covenant. Serina oversaw the destruction of a Super-Scarab and controlled the repairs to the Spirit of Fire.

She is constantly squabbling with Anders over who is smarter. Despite their agreement to disagree, Serina did remind Anders that she controls every system on board the Spirit of Fire - including life support. This grim reality is often shown to many an unwary officer who dares challenge Serina's judgement on a tactical situation regarding her ship.

After the crew spent 30 years in cryosleep following their adventures, Serina decayed and eventually took herself offline permanently. Deeply saddened by her loss, the crew were left without an AI until they had the good fortune to find Isabel on the Ark.