Step one: Play Mogu Cultist (1 Mana) with Embalming Ritual (2 Mana), Grave Rune (6 Mana) and Shadowy Figure (8 Mana) on it.

This will give you:

1. Mogu Cultist with reborn and deathrattle: summon two more reborn Mogu Cultist
2. Shadowy Figure (as a 2/2 Mogu Cultist) with reborn and deathrattle: summon two more reborn Mogu Cultist. 

Step two: Play Breath of the Infinite (11 Mana).

This will give you 6 Mogu Cultist on the board and the 7th Mogu Cultist is played from hand (12 Mana).

Step 3: If possible a Vivid Nightmare is used for the full 40 dmg combo wombo (15 Mana).

This is a 12 or 15 mana combo and as such:

For two Highkeeper Ra you need Fate Weaver to hit 5 combo pieces, for one Highkeeper Ra only 2 combo pieces.

Need to be holding:

2 Mogu Cultist

1 Shadowy Figure

1 Embalming Ritual

1 Breath of the Infinite

1 Vivid Nightmare

1 Grave Rune

I built this with more of a draw heavy / miracle priest shell, but you could also try control.