Magic

Divine Magic
Divine magic comes from the power of belief. If someone believes in something “Divine” it becomes Divine, tapping into the multiverse to create a source of power the person can use. So if a person who believed in a god so completely they would become essentially a cleric or at least capable of lower tier divine magic.

Your God = whatever the person thinks is their god. Through this belief and faith  they are empowered.

Leveling up as a cleric will essentially  mean your faith in the being you think exists becomes stronger and you become more well trained in using this wellspring of magic.

Thus to create a cleric in this setting, name your god and define what you  think they would be like and what domains they would encompass.

Druidic or Primordial Magic
The magic of druids or of the earth comes from the planet itself. The energies of the universe suffuse the planet and druids know how to manipulate this energy. When a druid summons creatures they are calling to the nearby by plane of Moonshore. Moonshore is the life filled counterpart to the Tenebric Maze.