If I play a Reaction Spell (Gust) that returns a unit (Noxian Drummer) to hand, can I negate its triggered effect that plays a token on the battlefield?

Ruling: Yes, you can negate the effect. When Gust returns Noxian Drummer to hand before its triggered ability resolves, the ability cannot determine where "here" refers to since the Drummer is no longer at the battlefield location, causing the ability to resolve with no effect and no token is created.

Sequence:

• Opponent declares moving Noxian Drummer to the Battlefield
• Noxian Drummer's ability triggers and goes on the initial chain
• You play Gust as a Reaction before the trigger resolves
• Gust returns Noxian Drummer to hand
• Noxian Drummer's ability resolves but cannot determine where "here" is
• The ability resolves to no effect and no token is made

Nuances:

• Spells in Riftbound re-evaluate legality at resolution
• If the battlefield gave Drummer +1 might as a passive effect, you would not be able to target it with Gust (which targets units with 3 or less might) by the time you could play it