Couple random thoughts meant as food...
My setting has sort of tiers of 'godhood'.
First, you have an unknown creator. Everyone knows
something created the 'beginning' after all right? But no one can say for sure who or what.
Then you have what are believed to be 'knowable' gods.
1. First are really Big subjects, like Good and Evil or Creation and Destruction (or Entropy). They rarely interact directly with the world (so far as anyone knows). They have no true physical form other than that which they project (think Avatars). These are true gods. They are immortal.
2. There are the elements; Air Earth, Fire, Wind and maybe Light and Darkness. They are largely set apart from all the others and tend to simply be pure to their element. The idea of 'worship' of them can be combined with other forms. Maybe a deity of the forest (if there is one) uses Fire for both Life and Death. Maybe the god of the Sea's uses Air in addition to Water in it's sphere, etc. Basically the elemental powers aren't good or evil, they simply provide where their nature takes them. They are immortal, but they aren't really true 'gods'.
3. Next down you have 'ideas' like Love and Hate, Greed and Charity, War and Peace, etc. The more that idea is prevalent in the world the stronger they become and vice verse. These deities can be interacted with and can potentially even be killed.
4. Lastly you have very powerful mortals (who are commonly thought of as minor deities) who sort of act as conduits to the above deities. This is where Channeling and Mentalism collide. Mentalism is an individual using their own personal power to manifest 'magic'. Channeling is Channeling that power from worshipers to a deity. So in a sense Channeling is large amounts of gathered and focused sources of Mentalism. This is how 'mortals' become 'deities'.
Channeling users can also be individuals who obtain their power from living sources that are not gods, let alone even sentient in the usual definition. The best 'normal' example of this in some setting would be a Druid that obtains it's powers from the forest. The life force of the forest is what they draw their power from. Bigger forest, more power. Burn the forest down, no power. Think of the forest as a deity that is indifferent to anything other than it's own existence.
Now... a Paladin is a warrior that believes in and 'worships' one of those things.
1. Paladin of Destruction? He might just like to see things destroyed. They'd potentially be in any army to any cause.
2. Paladin of Life? They may protect travelers or animals in a forest or officiate a wedding.
3. Paladin of Light? They may guard an important light house.
They would all be guardians of their churches... and that church could BE the forest (although I'd probably just make Paladins of the forest be Rangers really).
So... what is a Paladin? It's a warrior for whatever religious beliefs it holds (and probably has magical powers related to it - a'la the Channeling Companion).