I would like some clarification on Mana Shield, which reads:

"X, Prevent the next X combat damage that would be dealt to your hero by allies this turn."

Can this be used to prevent damage from multiple attacks?

I guess the real question is can you use prevention between combats? Which I believe is no.

This will prevent any combat damage up to the amount X until the end of the turn. Here's an example.

I play Mana Shield on my opponents turn and my X=4.

He attacks me directly with an ally with 2ATK. I take no damage.

He plays Fire Blast and I take 2 damage because Fire Blasts damage is not combat damage.

He attacks me directly with an ally with 3ATK. I take 1 damage because the 3ATK here and the 2ATK from before is one more then X.

Hope that helps.

It does, thanks. This is very powerful if you have a lot of resources.