Best way to deal with ethereals en masse?

[Pocus]

if the etheral units are magic, then you have some nice spells in astral to destroy them (opposition or a group of ether warriors for exemple).

If they are etheral and not magic and you dont have elemental spells, then you are better in summoning creatures that strike with a magic weapon. But you speak of being Jotunheim, so water or astral is always an option.

Tell us also what etheral units he has.