Can I exhaust 3 Chemtech Cask for 1 spell played during the enemy's turn?

Question

Accepted Answer

Yes — each Chemtech Cask you control that is ready will trigger separately when you play a spell on an opponent's turn, and you may exhaust each one to pay that ability's cost to create a Gold gear token for each Cask. You cannot exhaust the same Chemtech Cask more than once, and any Cask that is already Exhausted or otherwise unable to be Exhausted cannot pay the cost for its trigger.

When you play a spell on an opponent's turn, each ready Chemtech Cask you control generates its own trigger. Each trigger is finalized separately, and the cost within the trigger (“exhaust me”) must be paid for that trigger individually. Therefore you may exhaust three different ready Chemtech Cask to produce three Gold gear tokens (one per resolved trigger), but you cannot exhaust a single Chemtech Cask multiple times to pay multiple triggers. [333] [FAQ:unleashed#1] [FAQ:unleashed#3] [414.4] [414.1.b]

You play one spell during an opponent's turn (this is legal only if that spell was allowed to be played then). That play creates a Chain because a card was played. [333] Each separate ready Chemtech Cask you control sees the event 'When you play a spell on an opponent's turn' and creates a separate triggered ability Pending Item on the chain (each Cask’s trigger is its own chain item). [333] [FAQ:unleashed#1] During finalization for each triggered ability, the controller chooses whether to place that trigger on the chain. The 'you may' is the decision to add it; the instruction 'exhaust me to play a Gold gear token exhausted' is a cost within the trigger and becomes the base cost to finalize that triggered ability. [FAQ:unleashed#1] [FAQ:unleashed#3] To finalize any given Cask trigger, you must be able to pay its cost — exhaust that specific Chemtech Cask. If the Cask is already Exhausted or otherwise cannot be Exhausted, you cannot pay that trigger's cost and therefore cannot finalize that trigger. [414.4] [414.1.b] Because each Cask trigger is separate, you may finalize multiple of them (exhausting each corresponding Cask) to produce multiple Gold gear tokens. You may not use the exhaustion of one Cask to pay another Cask’s trigger. [FAQ:unleashed#3] [414.4] As the triggers resolve, each will create the Gold gear token as its rule text instructs when that triggered ability resolves.

If one or more Chemtech Cask are already Exhausted before finalization, those individual triggers cannot be finalized because the exhaust cost cannot be paid. [414.4] [414.1.b] If something else Exhausts or removes some of your Chemtech Cask in response before you finalize all triggers, later triggers for those now-unavailable Casks cannot be finalized for lack of cost. Order of finalization matters. [FAQ:unleashed#3] [414.4] If you were not the one who played the spell (for example the opponent played the spell), the trigger condition on Chemtech Cask ('When you play a spell on an opponent's turn') is not satisfied and no triggers are created. This ruling depends on whose action actually met the trigger condition. If the spell you played on the opponent's turn was illegal or undone during finalization (so the spell play never finalized), the Cask triggers would not be created because the triggering event did not successfully occur. [FAQ:unleashed#3] If the rule text of Chemtech Cask or the spell creating the event is altered by a replacement effect or other effect that changes who 'you' refers to, those changes could alter whether a trigger is created; that requires examining those replacement effects specifically.

Why this is allowed: The trigger on Chemtech Cask is a separate triggered ability tied to that specific permanent. When you play a spell on an opponent's turn, each ready Chemtech Cask you control will produce its own trigger and those triggers become Pending Items on the chain. The 'you may' and the 'exhaust me to …' in the card's text function as the decision and the cost-within-instruction for the triggered ability; per the triggered-ability finalization rules, that exhaust is the cost you must pay when finalizing that trigger [FAQ:unleashed#1] [FAQ:unleashed#3]. Exhausting is a cost that must be pay-able at finalization time [414.4], and a permanent that is already Exhausted cannot be Exhausted again [414.1.b]. Because each Cask's trigger is distinct, you can pay each one separately by exhausting each distinct ready Chemtech Cask, producing one Gold gear token per Cask whose trigger you finalize. You cannot, however, exhaust the same Chemtech Cask multiple times to pay multiple triggers, and any Cask that is not ready or is removed/exhausted before you finalize its trigger cannot be used to pay that trigger [414.4] [414.1.b].