Xtra HERO (X・HERO, Ekusutora Hīrō) is a sub-series of the "HERO" archetype comprised completely of Link Monsters. It is the first, and currently only, sub-group of the "HERO" archetype that has not been used by any character in any of in the anime or manga, and is the first "HERO" theme to be introduced since the GX Era (excluding the single, illegal "Entertainment HERO" monster).