Arathmetics

So this is pretty much my first draft on this deck, but I already had some serious fun with it.

The core of this deck is the synergy between the relics, the life gain and the vast amount of gunfodder units that can be fusioned into all-out killing machines.

Your core is Rat Cage, which will flood your board easily and Fearbinder, which transforms those pesky rodents into pure nightmarefuel while eliminating their no-block-malus. Marionettes work fine for this end aswell, but take care that you sacrifice all the marionettes on your board for a fearbinding.

Some more synergies:

Xenan Obelisk is an all-out monster in this deck, as Fearbinding will triple its bonus. It's basically Fear's Sum = (Unit1+Bonus)+(Unit2+Bonus)+Bonus. Use it as soon as you can!
Blood Quill and Excavate let you play your deck from both sides.
You can always sacrifice an Araktodon Egg for Consuming Greed
Lethrai Courtiers, Power Stone and the odd Mask of Torment ramp your power up to infinity and beyond, making the constant use of your relics more profitable.
Unless you have the Etched Monolith on board, always fearbind after attacking, this opens your new unit for blocking and allows it to attack the very next turn.
Since you sacrifice your units for Fearbinding, you can always return your ingriedients for even more fearbinding (or to trigger their summons/ultimates once more.
This also means you have a steady influx of cards to your void, making units like Umbren Deathwatcher, Soul Collector viable side-deck cards. You can also consider Pillar of Dreams, though this is mostly a worse form of Katra, the Devoted.