These spells are adopted from the Call of Cthulu game system. The magic has no spell level, and so can be taken at any time, has incredibly powerful or unusual effects, and erodes your very body and mind when you use them. Each spell has a cost which must be paid immediately upon casting the spell, usually in an ability score and a loss of Sanity.
Old-One magic is long lost, alien magic, and those who discover it are usually quickly driven insane upon using it. As such, any cache of Old-One magic which is found is very sparse in it's content, 3 or 4 spells at most, although more commonly it is just one spell at the end of someone's normal spellbook, usually followed by pages of insane scribbling. Spells will almost never have the same names, as their actual name is so alien that it is extremely vague and difficult to translate into any of the known languages.