It's been my belief that the Master had the original 13 incarnations used, with Delgado being 12 and Pratt/Beevers being 13 and everything afterwards being stolen bodies, with the death of Rogers (sucked into the Eye) being the ending of him until he was resurrected by the Time Lords and given the MacQueen body who travelled back in time to continue to mess with the Seventh and Eighth Doctors. Afterwards he regenerated into his "asian child" incarnation and fought alongside the War Doctor and at some point changed into Jacobi who fought in the War too and then transformed into a human. Then Simm, then Gomez.