Flying High Sentinels of Arashin gets +1/+1 for each other creature you control with a +1/+1 counter on it. {3}{W}: Put a +1/+1 counter on target creature.
2014-09-20
High Sentinels of Arashin gets +1/+1 per creature, not per +1/+1 counter. It doesn't matter how many +1/+1 counters are on any other creature you control as long as there's one or more.
2014-09-20
The activated ability can target and put +1/+1 counters on High Sentinels of Arashin itself.