Alright before I start heavy-lifting with the CS, I'd like to see if this is ok. How would you all feel about a God of Infinity and Impossibility joining you?
The God would be sort of considered an "outsider" even among other Gods and be rarely worshiped by mortals. As a matter of fact he isn't even that well known. He would go by the title of "The Outsider, The Stranger, Lord of Oblivion". His domains and powers would include things regarding impossibility and infinity (duh) such as the infinite space, a bottomless pit, the largest or the smallest number in existence, etc.
His primary attribute would be madness and fear; madness to represent the insurmountably ridiculous and impossible existence (such as an infinitely large number), fear since any mortal's most primal emotion to the unknown starts with fear. If a man falls into the ocean and sees an infinite black pit of dark waters beneath him, and he feels fear, this God would be the one who's responsible for such and be "with" him.
On the other hand, he is unknowingly somewhat worshiped by intellectuals such as scientists since the exploration of the unknown sheds light on the real nature of what seems impossible. However, he enjoys presenting an infinite number of challenges to be solved to those who dare challenge him in this manner. And eventually, this produces mortals who are mad on seeking out the true nature of this God - also known as knowledge beyond the possible (mad scientists/wizards anyone?).
Ofc I will get more details up with the main cs but this is the idea i'm rolling right now.
Assallya