This is the Neviilz Summoning Stone Old Gods Mage Deck he’s used to 
climb on ladder.
Summoning Stone – ‘Whenever you cast a spell, summon a random minion of the same cost’.
The aim of this deck is to get the summoning stone on the board and start casting spells. The value you get from the random minions can be insane and will turn a game in your favor with a little RNG!