Jon Snow, The Relentless

First strike, vigilance, undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
When Jon Snow, the Relentless dies, put a +1/+1 counter on each other creature you control.
"A man of the Night's Watch used one of these Dragon glass daggers to kill a walker."