Riftbound Stun

None of the 23 cards with Stun print a reminder explaining it, so there is no official wording to quote here. Rather than guess at the rule, the cards themselves are below.

23cards4median energyEUR 0.02cheapest

Which domains get it

Calm10

Order8

Chaos7

Which sets print it

Unleashed · 15Radiance · 5Vendetta · 3

Cards that mention Stun

These do not have Stun themselves, their rules text refers to it.

Eclipse Herald

When you stun an enemy unit, ready me and give me +1 might this turn.

Facebreaker

[Hidden] (Hide now for any rune to react with later for 0 energy.) [Action] (Play on your turn or in showdowns.) Stun a friendly unit and an enemy unit at the same battlefield. (They don't deal combat damage this turn.)

Gangplank - Naval

[Empower] Body runeBody rune (Body runeBody rune: Empower me. Use only if not Empowered.) [Empowered][>] If a spell or ability that chooses me would stun me, give me -might, or return me to hand, give me +3 might instead.

Gangplank - Naval

[Empower] Body runeBody rune [Empowered][>] If a spell or ability that chooses me would stun me, give me -might, or return me to hand, give me +3 might instead.

Gangplank - Naval (Judge Promo)

Leona - Determined

[Shield] (+1 might while I'm a defender.) When I attack, stun an enemy unit here. (It doesn't deal combat damage this turn.)

Leona - Determined

[Shield] (+1 might while I'm a defender.) When I attack, stun an enemy unit here. (It doesn't deal combat damage this turn.)

Leona - Determined

[Shield] When I attack, stun an enemy unit here.

Leona - Radiant Dawn

When you stun one or more enemy units, buff a friendly unit. (If it doesn't have a buff, it gets a +1 might buff.)

Leona - Radiant Dawn

When you stun one or more enemy units, buff a friendly unit. (If it doesn't have a buff, it gets a +1 might buff.)

Leona - Radiant Dawn