Have

Endless One

This creature enters with X +1/+1 counters on it.

Hangarback Walker

This creature enters with X +1/+1 counters on it.
When this creature dies, create a 1/1 colorless Thopter artifact creature token with flying for each +1/+1 counter on this creature.
{1}, {T}: Put a +1/+1 counter on this creature.

Pawn of Ulamog

Whenever this creature or another nontoken creature you control dies, you may create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this token: Add {C}."

Colfenor, the Last Yew

Vigilance, reach
Whenever Colfenor or another creature you control dies, return up to one other target creature card with lesser toughness from your graveyard to your hand.

Ugin's Conjurant

This creature enters with X +1/+1 counters on it.
If damage would be dealt to this creature while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from this creature.