Hi!

An attachment card with a certain sphere of influnece (ex: tactics) can be attached to an hero/ally that has another sphere of influence (lore, spirit, leadership) or it is restricted to be attached only on a hero/ally with the same spehere of influnece ?

An event card with a certain sphere of influence can affect other heroes/allies with different sphere of influnece?

Thank you!

There are no restrictions based on sphere unless the card specifically says so.

So only to get in play an attachment/event card you need to spend resources from a hero or heroes with the same sphere of influence? This is the only restriction for attachment/event cards to be brought in play?

Yes, the resource match is just to play it. You could even attach it to another players character

Thank you!