Ragnarok (ライナロック Rainarokku, lit. Linerlock, also known as Rainarok) is a Tome that is introduced in Fire Emblem Gaiden. It is the strongest Black Magic spell in its original incarnation, dealing heavy fire-based damage to enemies. Only Celica and Dyute can learn this spell.
Ragnarok reappears in Fire Emblem Fates as a tome of great power and high weapon rank. Smiting enemy targets with devastating plumes of fire, Ragnarok is essentially the tome equivalent of a Silver weapon.
HP Cost is -10
Ragnarök was the mythological Norse "apocalypse" that brought about the deaths of all the Gods and humans (Ragnarök literally means "the end of the gods"), save two humans who restart the race. It was embodied by events such as widespread fire or a great deluge.