Duthru, Witch-Maw Nephilim

When you cast a spell put a +1/+1 counter on Duthru, Witch-Maw Nephilim
If Duthru, Witch-Maw Nephilim has 10 +1/+1 counters on it, it also has trample
I Duthru, Witch-Maw Nephilim has 15 +1/+1 counters on it, it also has annihilator 1 and fear