Does Kennen, Keeper of Balance stun when removed from...?

Question

Accepted Answer

No — Kennen, Keeper of Balance only attempts to stun as part of its triggered ability “When you play me or I attack, you may pay :rb_energy_2: to [Stun] a unit.” If that trigger was created (e.g., Kennen attacked or was played) you may still pay the energy and stun a legal target even if Kennen, Keeper of Balance leaves the battlefield before the triggered ability resolves. However, any benefit that depends on Kennen being “here” (like “While there's a stunned enemy unit here, I have +2 :rb_might:”) will not apply if Kennen is no longer at that battlefield when the stun is applied. If there are no legal targets when the ability resolves, the stun cannot be performed.

The stun is produced by Kennen’s triggered ability (when played or when it attacks). Once that trigger exists on the chain you may finalize it and pay its cost (pay 2 energy) and stun a legal target even if Kennen, Keeper of Balance was removed from the battlefield after the trigger was created. The “+2 :rb_might: while there's a stunned enemy unit here” only applies if Kennen is at the same battlefield when the stunned unit is present.

Kennen’s ability text is a triggered ability that reads 'When you play me or I attack, you may pay :rb_energy_2: to [Stun] a unit.' The trigger condition (When you play me or I attack) creates a pending triggered ability on the Chain when that event occurs [FAQ:unleashed#1] [333]. When the trigger is being finalized, the 'you may' and the cost within instruction (pay :rb_energy_2:) are treated as the decision to place the item on the chain and the cost to be paid during finalization, respectively [FAQ:unleashed#1] [FAQ:unleashed#2]. If Kennen, Keeper of Balance leaves the battlefield after the trigger was created but before the triggered ability finalizes, the trigger is still present and may be finalized as normal; the controller may choose to pay the energy cost and choose a legal unit to stun if one exists [333] [FAQ:unleashed#2]. Stunning itself is a Limited Action performed by the effect; the effect will render the chosen unit Stunned provided that unit is a legal target at finalization [423] [359.3.e.12]. If there are no legal targets at resolution (for example, no units on the board), the instruction to stun cannot be executed and will be ignored as much as possible [359.3.e.12] [359.3.e.11]. Any continuous or conditional benefit that refers to 'here' (for example, 'While there's a stunned enemy unit here, I have +2 :rb_might:') requires Kennen, Keeper of Balance to be at that battlefield when the stunned unit is present; if Kennen left, that bonus will not apply even if the stun occurs elsewhere or while Kennen is gone.

If the ability had required Kennen itself as part of the cost (e.g., 'exhaust me to'), and Kennen had left play or was no longer able to be exhausted at finalization, then that cost would be illegal and the ability could not be finalized as paid. (This is not the case on Kennen, Keeper of Balance because the cost is only payment of energy.) If the stun target is checked and becomes illegal during resolution (e.g., the only possible target is removed), the stun cannot be applied and that portion of the effect is ignored [359.3.e.12]. If some replacement effect changes the way Kennen’s attack or play event is processed (not present in the provided context), it could prevent the trigger from being created in the first place; then no stun attempt would occur [FAQ:unleashed#1]. If players are required to make choices when placing the trigger on the Chain (e.g., targets chosen at that time by templating), those choices and the legality checks occur during finalization; if targets must be chosen then and the necessary objects no longer exist, you cannot choose them [FAQ:unleashed#2] [359.3.e.12].

The text on Kennen, Keeper of Balance is a triggered ability: 'When you play me or I attack, you may pay :rb_energy_2: to [Stun] a unit.' Triggered abilities create pending items on the Chain when their trigger condition is met [333]. The rules and clarifications for triggered abilities explain that a 'you may' appearing next to the trigger/conditional is the controller’s choice to place the ability on the chain, and any cost that appears next to that 'you may' becomes the base cost paid during finalization of that triggered ability [FAQ:unleashed#1] [FAQ:unleashed#2].

Because the stun is the effect of that triggered ability, once the trigger exists on the chain you may finalize it, pay the :rb_energy_2: cost, and stun a legal target even if Kennen, Keeper of Balance left the battlefield between the trigger’s creation and its resolution. Stunning is a Limited Action performed by the resolving effect, and it does not inherently require the source permanent to still be present unless the cost or effect text specifically referenced the source as part of the cost (for example, 'exhaust me to...') — in this case the only cost is energy, so Kennen’s continued presence is not required to pay that cost or to apply the stun [423] [FAQ:unleashed#2].

However, practical limitations apply: if there are no legal unit targets at the moment the triggered ability resolves, the stun cannot be executed and that part of the instruction is ignored as much as possible [359.3.e.12] [359.3.e.11]. Also, the printed secondary clause on Kennen, Keeper of Balance — 'While there's a stunned enemy unit here, I have +2 :rb_might:.' — depends on Kennen being at the same battlefield ('here') as the stunned unit. If Kennen left the battlefield before the stun was applied (or was stunned elsewhere), Kennen will not gain that +2 might because the condition 'there's a stunned enemy unit here' will not be true for Kennen’s location.

In short: the stun itself can still be applied after Kennen, Keeper of Balance leaves play provided the trigger was created and there is a legal target when the ability resolves; the location-dependent might bonus will not apply if Kennen is no longer at that battlefield. This answer assumes no other unlisted replacement or continuous effects modify the trigger, cost, or target legality.