Hardened Scales
Mistcutter Hydra
Master Biomancer

Arnie cast Mistcutter Hydra with X=6 and he controls a Master Biomancer (with 2 power) and a Hardened Scales.

Does Hardened Scales apply once or twice to the Hydra's entry to the battlefield?

Edited Todd Bussey (Oct. 1, 2014 10:53:37 PM)

Mistcutter Hydra will receive only one additional counter. All of the counters the Hydra is entering the battlefield with are being placed on it simultaneously, so Hardened Scales sees all of them as one instance of placing counters, and will only apply once. The fact that two different replacement effects are causing those counters to be placed doesn't matter.