Can you Gust Blastcone Fae (played from hidden) before it gives your unit -2?

Ruling: No, gusting Blastcone Fae will not prevent its ability from resolving. The target is still legal because the ability doesn't care about Blastcone Fae's position on resolution.

Nuances:

• Hidden effects used to gain an implicit 'here' targeting restriction, but this is outdated information
• Hidden effects now follow the rule that targets must be chosen from options at that battlefield, unless the ability explicitly restricts targeting differently
• Moving the targeted unit (not the Blastcone Fae itself) would void the ability, as the ability does care about the target's position