In a polytheistic setting, worshiping multiple gods is not only doable, it is standard practice. As a cleric you would hold one of those gods as your patron, but you would not dishonor the other gods by avoiding their services and festivals.
Can clerics not worship a god?
No, a cleric doesn’t need to worship a god. Eberron has a couple religions that don’t have any kind of divine entity at all, and the gods of that setting (probably) don’t even actually exist.
Can clerics change domains 5e?
As stated above, no there’s no change in switching either Deity/Domain.
Can you be a Paladin of an evil god?
To answer your question, yes, a Paladin can be evil. What defines the Paladin in 5e is their individual oaths, and how you express the ideas of your character oath. There are a few oaths that are tailored for the concepts of evil, but even then, it is still not dictated that the character should be evil.
Can a cleric have divine power without it being?
You may not have chosen a god but the god choose you. Your player may think he got his power by being struck by lightning, but maybe it is how the god chooses his followers. Most spells can be rewritten to instead of calling to a god, he calls to his inner self (spoilers: which is calling to his god).
Can a cleric call to a God instead of a god?
Most spells can be rewritten to instead of calling to a god, he calls to his inner self (spoilers: which is calling to his god). This way none of the spells need to be redesigned. The player just thinks hes doing it all himself. Mechanically speaking, there’s no real distinction between arcane and divine spellcasting.
Can a cleric be a paladin or a god?
A cleric, druid, or paladin can choose to follow a cause they passionately believe in as opposed to a deity. The PHB (see Appendix B) notes that it is perfectly acceptable for a DM to decide that there are no gods that are worshipped in his or her campaign:
Where do clerics get their powers from in RuneScape?
It might be that this Cleric gets their powers from a deity of nature, who chose to give them their power, even though the Cleric doesn’t follow them. Or maybe the storm unleashes something inside of them. Alternatively, Paladins follow Ideals and Oaths, even though they are granted their powers from deities.