State-based timing (Elesh Norn and opponent critters)

[TheWhiteDragon]

I have an Elesh Norn in Play.  My opponent has a Myr Enforcer (now 2/2 thanks to Norn).  Can my opponent cast Arcbound Ravager and sac other artifacts (like mox opal) to make Enforcer bigger, or does the Ravager die as soon as it hits play without time to use his abilities?
Similarly, if my opponent has a 3/3 Ravager before Norn hits, can he cast Ornithopter and sac ravager to give it +3/+3 or does the Ornithopter die immediately???

[The Atog Lord]

A creature with 0 toughness (such as an Ornithopter when the opponent controls Norn) is never actually in play when the controller has priority. So, the opponent cannot sacrifice the creature to Ravager (or sacrifice Ravager itself). However, the Ravager's Modular trigger will still fire.

So, suppose the opponent has Elesh Norn in play and the player has a 2/2 Enforcer. The player casts Arcbound Ravager. As soon as Ravager resolves, before its controller regains priority, the Ravager enters the Battlefield and then enters the graveyard.  When the player gains priority, his Ravager is dead, but the Arcbound trigger is on the stack so he will be able to put a +1/+1 counter on the Enforcer.