It's Combo Time! The prerequisite is having 3 available to cast the artifact while it's in our hand, plus Vhal needs to have 5 or greater toughness and cannot have summoning sickness. You can check out our deck primer on Vhal for details on that!
1. Cast Staff of Domination for 3 (*this is the first point of interaction with the combo, where opponents can respond by removing Vhal or countering Staff of Domination while it's being cast*)
2. Tap Vhal for at least 5 colorless mana
3. Activate Staff of Domination for 3 to untap Vhal (*this is another point of interaction with the combo, where opponents can respond by removing Vhal or destroying the Staff*)
4. Staff of Domination's activated ability resolves, untapping Vhal
5. Activate Staff of Domination for 1 to untap the Staff (*this is yet another point of interaction with the combo, where opponents can respond by removing Vhal or destroying the Staff*), netting us 1 extra colorless mana
6. Demonstrate a loop which grants us an unbounded amount of mana