Does Unyielding Spirit prevent damage from Challenge and similar spells that make units deal damage to each other?

Ruling: Unyielding Spirit does not prevent damage from Challenge or similar spells (like Gentleman's Duel). These spells cause units to deal damage to each other, not the spell itself dealing damage.

Nuances:

• Unyielding Spirit only prevents damage dealt by spells themselves
• It does not interact with removal spells that don't deal damage (like Hidden Blade, Cull, Rebuke)
• This follows the same ruling as Void Gate, which does not add damage to Challenge because the units are dealing the damage, not the spell
• Unit abilities that deal damage (like Green Yas/Shark) are prevented by Unyielding Spirit, but Challenge is treated differently because it makes units deal damage to each other