Discussion Forum

I'm not quite sure what you're asking. Lullmage Mentor is able to block attacking creatures, just like any other creature you control can, so long as he is untapped at the time you declare blockers.

If you mean, can he counter creature spells? If you have seven untapped Merfolk, then yes, you can tap them and counter any spell you want. You can only counter a spell while it's on the stack, so you cannot tap seven untapped Merfolk to counter a creature that is already on the battlefield (if that's what you meant, too).