Vanaheim Realm Bonus one of the best. It’s described as “Mana of all enemies reduced by 5/10/15% when a Vanaheim hero dies”
The strange thing is if a hero is immune to a mana reduction by a buff (I’m looking at you dear Poseidon!) or by a innate ability (Seshat, it’s you) this realm bonus can be resisted.
So this effect can be countered with a buff or ability, this makes me expect that if there is an active taunt (Queen of Hearts, Black Knight and Krampus) protected heroes shouldn’t be affected. But it doesn’t work at all, realm bonus affects all heroes.
I hope this wasn’t the expected behaviour at all.