Can you use Repulse to counter Atakhan's 'When I attack' ability?

Ruling: No, Repulse cannot be used to counter Atakhan's "When I attack" ability. Atakhan's ability does not choose a unit; it forces the defending player to kill one of their units, which means it does not meet Repulse's requirement to counter an ability that "chooses" a unit.

Nuances:

• Repulse specifically requires countering an ability that chooses a unit
• Atakhan's ability targets the player and makes them perform an action, rather than choosing the unit itself
• The distinction is between an ability that chooses a unit versus an ability that forces a player to make a choice