Dusk Urchins -
Whenever Dusk Urchins attacks or blocks put a -1/-1 counter on it.
4/3
What's the timing of this trigger? Can I attack for a first time for 4, then put the counter on it, or is do I have to put the counter on it as soon as this is announced that it's attacking?
You announce that it's attacking at the beginning of the Declare Attackers Step, and then it triggers. The triggered ability will go on the stack just before you gain priority, and then it will resolve (excluding Stifle etc) in the same step. Unfortunately, that's long before you reach combat damage, so you will attack for 3, not 4 (excluding Giant Growth etc).
