Eredan

Does she work with cards such as menacing sky, mastery, etc?

Do you mean or ? Mind you, your answer is no for , since they both aren't pirates and won't play the pirate cards menacing sky makes, but yes for mastery and maybe for etc.

the effect of +1 to spells of ishaia works for damage, healing, discard (almost everyone), stats buff

Yeah, I noticed. Got Ishaia and tried putting her together with mastery/menacing sky (which happens by using a savage cloak on the marquis) - doesn't work :\ sadly. Shouldn't they rework it so that when she uses a spell that makes another, it would actually make 2, not one copy?

no, that would be insane