A deity is a being of great power that controls some aspect of mortal affairs, referred to as the god's portfolio.
All deities are either elevated to their positions by Ao (the overseer) or are approved by Ao to be worshiped in the Realms, in the case of interloper deities. No divine power found a permanent faith and power base without his approval, though there were cases of short-term semi-divine beings who gathered faith from worshipers without being deities. The most noted example of this was the various fiendish cults that had arisen. In at least two cases, the worship from these cults had provided enough power or filled a niche that was not otherwise filled, and the fiends in question had become deities in their own right. Both Gargauth and the minotaur deity Baphomet became deities by building on the power foundation of a fiendish cult.
Worshipers are necessary for the continued existence and powers of a deity. The numbers and fervor of a god's worshipers determine in large part the power of the deity. Deities without worshipers or who are fading in popularity fade in power, and in extreme cases can even die from neglect.
The deity descriptions within my world of Abios have been altered specifically to fit my world. While I try to hold true to the original canon of Forgotten Realms and 2e through 5e D&D, certain details had to be changed in order for things to "fit". For more information on the types, abilities, ranks, and pantheons of deities, visit the Forgotten Realms Wiki by clicking here.