Short question:

I play a Mask Attachment card on a opponent's character (-2 Skill).

Next turn he plays event: sacrifice Mark card to gain "something".

Can he sacrifice card that I have played on him?

Yes, you remain the controler of the attachment, so you can sacrifice it.

Marius said:

But the opponent can't though, right?

The_Big_Show said:

Nope; They can sac the character to some effect though. But they can't sack your attachment itself.

Never mind. I read the OP's question wrong.

wait isnt the question whether the other player can sac the mask card for the event?

Veross said:

Let's try to give a a full answer to your short question:

The other player(s) cannot sacrifice that card (the Mask), only you can. After all, you played it.

But, the other player can sacrifice their character for the benefit, making your attachment pointless.

(Todd grumbles about people too lazy to type an extra couple of letters in their replies: "sac", "OP", "TLA", "RSVP", etc.) (Wait, does "etc." count? Crap!)

yes etc counts, this is the full spelling 'et cetera', also let's is cutting corners too, haha lazy people!

y cnt th3y rite so it can b red???