Hearthpwn

Some notes:

Keleseth is run not necessarily because it is essential but because none of the 2-drop minions available for Priest are strong enough.

The wildcard in this deck is Kabal Songstealer. What this deck really lacks is removal, because of the lack of spells. The main weakness of this deck is being unable to answer threats because of the lack of removal. Notably, direct damage (proactive and reach) is better than hard removal (reactive and complements a deck with less board presence) in an aggro deck.

The meat of the deck is the Keleseth neutral tempo package, complimented by Priest specific minions such as Kabal Talonpriest, Lightwarden, and Northshire Cleric.

The sheer late-game value of this deck (notably with Spiteful Summoner and Mind Control) can even out-duel many control decks.

Grand Archivist seems to be a really slow, win-more card. You really want it to cast Mind Control, but you also need a lot of spells in your deck to make it work, because it actually consumes the spell. It also makes your Spiteful Summoners less consistent. Archivist is bad if your opponent has any significant board presence. Also because Archivist takes your entire turn, unlike Scalebane, it is much harder to protect it with taunts.