Gavony Unhallowed

• WWizards of the Coast2016-07-13
  Official Ruling
  If Gavony Unhallowed and another creature you control die simultaneously (perhaps because they were both attacking or blocking), Gavony Unhallowed won’t be on the battlefield as its triggered ability resolves. It can’t be saved by the +1/+1 counter that would have been put on it.

Rulings via Scryfall