May 18, 2016
I activate Jalira, Master Polymorphist's ability, paying the cost by sac'ing a creature with Modular. Does the Modular trigger go on the stack before the Polymorph ability, which would then allow me to put +1/+1 counters on the creature that enters the battlefield (if it is an artifact creature)?
Because sacrificing the creature is a cost to activate the ability, then the triggered ability will have come and gone by the time the activated ability resolves. You won’t be able to put the counters on the new creature because it’s not on the battlefield yet.