When I control Silumgar, the Drifting Death and I have 3 dragons attacking, do creatures my opponent control get -1/-1 until the end of the turn or will it multiply 3 times, one for each dragon, ultimately making them -3/-3 until the end of the turn?
Your opponent's creatures will get -3/-3. If it were otherwise, the ability would be worded something like "Whenever one or more dragons you control attack..."
It triggers once for each dragon, so three times in total for -3/-3
Currently Playing:
Legacy: Something U/W Controlish
EDH Cube
Hypercube! A New EDH Deck Every Week(ish)!
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)