Fashioned from soft yet still quite durable lambskin, this piece of parchment gives a faithful divine spellcaster of a specific religion a hint about what spell may be useful for that day. Each day, when the owner prepares spells in the presence of the guiding vellum, the name of one specific divine spell which the owner already has the ability to cast appears on its surface. This represents a spell which should prove useful for the tasks in the next 24 hours. Each guiding vellum is associated with one level of divine spells and only shows a spell of that level. For example, if a cleric caster has a 3rd-level vellum and the GM expects the character to face invisible opponents later that day, the vellum shows the name “invisibility purge” (a 3rdlevel cleric spell); if the opponents are using poison and the cleric has a 2nd-level vellum, it would show the name “delay poison.”
A caster can only use one vellum of a particular spell level each day (using two 1st-level vellums gives the same result), but using vellums of different spell levels works normally. Each vellum works only once per day. A guiding vellum normally does not work for a character not of the item’s specific religion; some religions add additional magic so a vellum used by a hostile or rival faith provides misleading spell suggestions.
The key aspect here is that it says "faithful divine spellcaster". It does not say "spellcaster who gains his magic from a deity", as some other effects hint at.
It doesn't matter if your actual magic isn't strictly coming from a deity. These items should work for you absolutely perfectly.