IG-11, was originally a bounty hunter during the New Republic Era. During one of its mission to kill Grogu, it was destroyed by Din Djarin. Kuill would later retrieve the droid and reprogram it to serve his moisture farm. After the master's demise, it was reprogrammed to protect Grogu and sacrificed itself to provide cover for Din Djarin and Grogu.
It was later repurposed again by a group of Anzellan droidsmiths to form IG-12. The Anzellans made the droid to specifically fit Grogu to operate. IG-12 was eventually destroyed by Moff Gideon's forces during a mission to retake Mandalore. After the battle, IG-12 was again salvaged to create IG-11 Marshall.
For more info on IG-11, visit the entire Wookipedia Article on IG-11.