FateTarnished Light Elden Ring & FateZero Crossover

The Tarnished Warrior messes up while using Miquella's needle and promptly manages to evict herself from her own world. Desperate to not fade away in the space between worlds, she manages to grab hold of a summoning ritual. Being somewhat familiar with the process, even if it was different, she manages to summon herself into the Fourth Holy Grail War in Fuyuki as a Servant.