(I DM very loosely rule-wise, copious amounts of improv, death to carry weight etc.; As such I am hoping you all will help me spitball my idea, expand upon it etc. I have the husk of the idea, but I'm a little mentally sore from all of the homebrewing.)

Long story short I'm running Convergence, a totally balanced Sci-Fi Fantasy Spelljammer campaign. In my cosmology I've slammed all official pantheons, planes, and realms into my world cosmology, and my own eldritch pantheon. The Void exists as the great nothing, the omniversal empty backdrop to reality, the Alt-F4 realm if you will.

Faith in nothing, believing in the void functions as a Catch 22, allowing clerics, paladins, warlocks, etc. to have a uniquely dangerous alternative to Gods and other Patrons. The core idea is the Nihilism Domain, which allows you to pick and choose from any domain and said domains' spells at a steep set of potential costs/risks with some merciful passive bonuses (Maybe) sprinkled in. It's essentially the Fuck all o' y'all option. I'm thinking one cost, one boon.

The costs/risks to choose or get chosen are:

-Null Exposure- Faith in the Void makes one vulnerable to possession by Voidspawn (Sometimes something emerges from the great nothing, be it small or realm-eating. They favor the faithful or Voidborne (Voidborne is a background I made, gives you bonuses but no soul, meaning permadeath and Null Exposure)).

-Hollow Blessing- You have a higher chance to find and encounter things Void-related.

-How Easy It Is To Let Go- When you die there is a 5 out of 1D20 chance your soul will pass turbulently into the void. This form of spiritual obliteration will cease your existence. This supersedes the spell Wish.

The maybe passives/boons to choose:

-Well Aware: You have advantage on perception and insight checks against all things Void-related.

-Uncanny Valley: Extra-planar beings are likely to not notice you and your smothered soul presence. In addition they may or may not be subject to the effects of Frightful Presence (DM decides when, if, and where. Also no I'm not stingy about proccing this effect frequently).

-Cease Thy Blithering: As an action, bonus action, or reaction you make a special grappling check with advantage against a target of your choosing that is adjacent to you. On a successful save this unique attack fails and nothing happens. On a failed save the target takes 2D20 40 magic damage that ignores all resistances and immunities. It takes 1D4 days for this ability to recharge.

P.S.-This post is too bloated to edit on mobile anymore, F.