3.5 Domains:

Knowledge

Madness

Mind

Mysticism

5E Domains:

Knowledge

Plexia seeks knowledge in all of its forms. So far so, it is said that she's driven herself to the brink of insanity with her wealth of knowledge.  Shes not a commonly worshiped deity, but she is prayed to for information, guidance, and before trials and tests. Many believers that genius and insanity go hand in hand use Plexia as an example, and it's become common to refer to an insane genius as a 'Plexiate', but only context can infer if it's meant as an insult or a compliment. Ironically, most 'Plexiates' never get the reference. Her symbol, the Closed Tome, represents her desire to log her knowledge, but not to let anyone see it. Needless to say, while her clerics and followers often meet those of Altru, they don't tend to get along much.