If Sett already has a buff, can you stack the triggers so Monastery of Hirana draws a card and then Sett's trigger refunds the buff?

Ruling: Yes, you can stack the triggers. When both Sett and Monastery of Hirana trigger simultaneously on conquest, you choose the order. You can resolve Hirana's trigger first (drawing a card and removing Sett's buff), then resolve Sett's trigger (which will buff him since he's no longer buffed).

Sequence:

• Both Sett's conquer trigger and Hirana's conquer trigger go on the chain simultaneously
• You choose to place Sett's trigger on the chain first, then Hirana's trigger
• Hirana's trigger resolves first, drawing a card and removing Sett's buff
• Sett's trigger resolves second, buffing Sett since he is no longer buffed

Nuances:

• Sett's trigger is added to the chain even if he is already buffed; it simply won't do anything if he's still buffed when it resolves
• Buffed units can always be targeted by buff effects (unless a card specifies non-buffed units), even if the effect won't do anything to them