1Activate Karn by paying , causing Staff of Domination to become an artifact creature until end of turn.
2Activate Grand Architect's first ability by paying , causing Staff of Domination to become blue until end of turn.
3Activate Grand Architect's second ability by tapping Staff of Domination, adding that can only be spent to cast artifact spells or to activate abilities of artifacts.
4Activate Staff of Domination's first ability by paying , untapping it.
5Repeat from step 3.
6Once you have infinite mana, you may instead tap Staff of Domination using its other abilities if it does not have summoning sickness.