mtg remove a counter draw a card Zameck Guildmage [Gatecrash Promos] o:remove o:counter o:draw o:+1 c!u

Casual/CommanderBramble Sovereign: Absolutely

At the beginning of each opponents upkeep, they lose 1 life and you put a -1/-1 counter on up to one target creature they control

Cursed Mirror catches any relevant ETB effects upon hitting the battlefield, and it doesn't take much to get extra value out of it

I'm hopeful that maybe Birthing Pod could power up some sweet combo-ish toolbox deck in the format, but I think there's a much higher risk that it is unplayable than of it breaking the format

my focus is on mechanical identity

The challenge involved wanting the monster themes to matter without making it a typal set in the way the Onslaught and Lorwyn blocks had been