Hello,
Savage Summoning has the following text:
“Savage Summoning can't be countered.
The next creature card you cast this turn can be cast as though it had flash. That spell can't be countered. That creature enters the battlefield with an additional +1/+1 counter on it.”
Savage Summoning allows us to cast a creature card with Bestow as though it had flash and we actually can choose to pay its Bestow cost after putting it on the stack. “That spell” references to whatever spell we get as a result: Aura spell or Enchantment Creature spell. Does “That creature” in the last sentence references to the resulting object on the battlefield or only references that object in case it is a creature?
As the effects that modify the way objects entering the battlefield are applied before the object actually enters the battlefield, I would guess that we'll get an Aura with a +1/+1 counter that has no effect while the Aura is attached to a creature. Is it true?
Thank you!

It will get a +1/+1 counter that has no effect (until it becomes a creature again).

“That creature” refers to the object as it enters the battlefield, no matter what its type is at that point. A +1/+1 counter on a non-creature permanent has no effect, but stays there. When the permanent becomes a creature, the counter has an effect again.

Daniel Kitachewsky
L3, Paris, France
Rules NetRep