Question About Extra Fire and Posion Damage

[watersky82]

For the first medal, it adds a certain amount of fire and poison damage.

Is it applicable to both spells and attacking units?

For example, red dragon, black dragon, bone dragon, royal snake, swamp snake, assassin will be able to inflict more damage?

Or poison skull, flame arrow, fire rain, fire ball will be able to deal more damage?

Or both?

And for weapon like Assassin Dagger that increase poison damge by +1, is the weapon useless if you don't have units that deal poison damage?

Or will equipping Assassin Dagger now give every of your unit a chance to inflict poison damage?