Fragarach

In Irish mythology, Fragarach (or Freagarthach), known as 'The Answerer' or 'The Retaliator', was the sword of Manannan mac Lir and later, Lugh Lamfada.

Forged by the gods, Manannan wielded it as his weapon before passing it on to Lugh (his foster son). It was given to Cúchulainn by Lugh, and later to Conn of the Hundred Battles.

It was said that no one could tell a lie or move, with Fragarach at his or her throat, thus the name 'Answerer'. It was also said to place the wind at the user's command and could cut through any shield or wall, and had a piercing wound from which no man could recover.

Science-fantasy author Patricia Kennealy Morrison uses Fragarach in her series The Keltiad the sword is used by several of her protagonists over the course of the series.

Fragarach appears in the Dungeons & Dragons module The Temple of Elemental Evil as a sword that never misses and "answers" any strike to the wielder with a strike of its own. It later reappeared in 4th Edition as a sword destined to slay Thrumbolg, a powerful fomorian lord.

In Hounded, written by Kevin Hearne, Atticus O'Sullivan wields the famous sword, and his possession of it is the cause of most of his troubles.

In the visual novel Fate/hollow ataraxia, the sword appears as the weapon of Bazett Fraga McRemitz. It is a weapon that, upon the activation of an opponent's strongest attack, reverses time and kills the enemy before they use their attack.

In the Digimon series, Fragarach is an extensible greatsword carried by Slayerdramon a Mega level Dragon Man Digimon.

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Wikipedia