this is probably a dumb question, but what is a realm bonus please?
As far as I understand it is essentially a bonus, more or less like family bonus, that works slightly differently.
Let’s make an example with this season 3 hero I have:
This is By-Ulf. It’s realm is the symbol placed at the bottom of the class symbol.
So his realm is the “blue” one (Niflheim realm) and it’s effect (for this realm) is explained in the card.
This case when one or more heroes of this realm (this case the “blue” Niflheim realm) has low health, than all enemies will lose accuracy -5 (if one niflheim low healt), -10 (if two), -15 (if three or more). If, for example, I use only by-ulf (so he is the only hero of Niflheim realm I am playing), this is what will happen: when he reach low health my opponent’s heroes will have -5% accuracy as long as he is low health (since he counts also himself in the effect).
Other realms works more or less the same way. Every realm has a different effect (we see Nilflheim realm effect as an example) but the logic is the one explained (effect is applied as many times as you are using more heroes of the same realm… more or less like family bonus).
Thankyou for your information.