For late achievement hunting this deck works really well. It's a mid-range Priest that relies on summoning and resummoning Haunting Nightmare to spam 4/3 tokens on board.

To counter Imp locks, handbuff paladins and other board-oriented decks you have Undying Disciple.

This deck also has a pretty decent card draw. This means you can end up with no cards in your deck - to leverage this, you have Rivendare, Warrider which also counts for achievement.

Achievements hunted:

• [Scare Tactics] - Play 120 cards haunted by Haunting Nightmare
• [Brain Food] - Restore 100 health with Cannibalize
• [A Graveyard Smash] - Summon 25 Undeads in one game
• [On a Pale Horse] - Destroy enemy hero 4 times with the Horsemen from Rivendare, Warrider

You can also add Sister Svalna for [10/10 Vision] - I don't have this card so it is not included in this deck.

Perks:

• Positive winrate in Bronze-Gold bracket
• You can go through your whole deck in most cases
• It's fun to play