Can a unit with Weaponmaster equip an equipment when played during a reaction/action window?

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Accepted Answer

Yes. A unit with Weaponmaster can have an Equipment attached when it is played during a Reaction/Action window. Weaponmaster explicitly allows you to pay an Equipment’s Equip cost and attach it to the unit regardless of the usual timing restriction on Equip abilities [821.1.b]. Playing a unit as a Reaction is permitted (Reaction allows play during Closed States) though it still obeys unit placement restrictions [813.1.c.1] [813.3.a].

When you play a unit with Weaponmaster (for example, Azir - Emperor of the Sands) during a Reaction or other Closed State timing, the Weaponmaster play effect may trigger and resolve to choose an Equipment you control and pay its Equip cost (with the Weaponmaster discount) to attach it to that unit even though Gear’s Activated Equip ability normally can only be executed in the Main Phase [821.1.b] [150.2]. The Equip ability is not being activated by Weaponmaster (the attachment happens as the Weaponmaster effect) [821.1.c.6]. If the chosen Equipment’s Equip cost can’t be paid or it can’t legally attach, it remains where it is [821.1.c.5].

You play the Weaponmaster unit during a Closed State using Reaction permissions (allowed by Reaction) [813.1.c.1] and you meet any placement restrictions for units [813.3.a]. The Weaponmaster play effect triggers "When you play me..." and becomes a pending chain item. When that trigger is finalized and later resolves, you may choose an Equipment you control and attempt to pay its Equip cost (with the Weaponmaster discount) to attach it to the unit [821.1.b] [821.1.c.2]. Because Weaponmaster’s effect explicitly permits paying the Equip cost and attaching regardless of the normal timing of Equip, the normal timing restriction on Gear’s Activated Equip ability does not prevent the attachment here (the Equip ability itself is not being activated) [821.1.b] [821.1.c.6] [150.2]. If the Equip cost can’t be paid, or the Equipment can’t legally be detached/attached, the Equipment stays where it is and the Weaponmaster attachment does not occur [821.1.c.5]. If you need more resources to pay the Equip cost while paying costs for the Weaponmaster effect, you may use Reaction Add abilities to add resources at the required moment (per rules governing paying costs and Add Reactions) [357.1] [429.3].

If the chosen Equipment has no Equip cost it cannot be paid and thus cannot be attached via Weaponmaster [821.1.c.4]. If the Equipment is currently Attached to something that cannot be detached or cannot legally attach to the Weaponmaster unit, it remains where it is [821.1.c.5]. Multiple instances of Weaponmaster trigger separately and may choose different Equipment (or the same target resolved separately) [821.1.c.7] [821.1.d]. Weaponmaster does not "activate" the Equipment’s Equip ability, so any wording that relies on activating that ability (as opposed to paying its cost to attach via Weaponmaster) does not apply [821.1.c.6].

Weaponmaster’s text is a play effect that explicitly allows choosing an Equipment you control and paying its Equip cost at a discount to Attach that Equipment to the Weaponmaster unit regardless of the normal Equip timing [821.1.b]. Reaction permissions allow you to play cards during Closed States on any player's turn, so playing a Weaponmaster unit during a Reaction/Action window is permitted (units still must be placed to your base or a battlefield you control) [813.1.c.1] [813.3.a]. Gear’s Activated Equip ability normally may only be executed during your Main Phase in an Open State [150.2], but Weaponmaster’s wording overrides that timing by making attachment part of the Weaponmaster play effect instead of an activation of the Equip ability [821.1.b] [821.1.c.6]. When the Weaponmaster effect resolves you attempt to pay the Equipment’s Equip cost (determined as if the Equip ability were being activated) and attach it; if the cost cannot be paid or the Equipment cannot legally be detached/attached, nothing moves [821.1.c.2] [821.1.c.5]. If you need to add resources while paying that cost, Reaction Add abilities may be used at the point resources are required per the rules for paying costs and Add Reactions [357.1] [429.3]. Therefore, playing a Weaponmaster unit during a Reaction/Action window can result in immediately equipping an Equipment via Weaponmaster, provided the Equipment is a legal target and its cost can be paid.