Moff Gideon, or just Gideon, is the main villain of the Disney+ series The Mandalorian. Gideon was a soldier in the Galactic Empire, who rose through the ranks to Marshal: By 9 ABY, he claimed the title of Moff and formed his own faction of the Imperial remnants, consisting of mercenaries and former Stormtroopers.
In Season 2, he finally succeeds in his goal of capturing Grogu aka The Child. However, in the season finale, he was defeated in combat aboard his light cruiser by Din Djarin, who had come to rescue Grogu. Djarin managed to take the Darksaber from Gideon during the fight and capture the Moff, taking him to the bridge of the cruiser, where Djarin's allies were waiting.
It is unknown whether Gideon was officially taken into New Republic custody or not after the episode's events, but it can be assumed that this is what happened after.