Elemental affinities
opposites across each other, related grouped.
Water Fire
Earth(sand) Air
Light Dark
Poison* Healing*
Gravity
Time
Space
*Nature is typically controlling plants and/or rarely (at low levels) animals.
both can be part of nature, although healing can also be light and/or water, and poison part of dark(occasionally fire but that's rarer).
Combined Affinities(rarer than usual ones)
Lightning:found in chaos, fire+light affinities
Magma: Fire+earth
Mud: earth+water
Cloud:air+water
Ice: water+air
Necromancy: dark+healing
Spacetime:Space+time+gravity
Summoning:Life+spacetime
Life: healing+light+poison(many life forms use toxins-snakes and frogs for example)
Death:poison+dark+healing(to kill you must know how to save)
Nature: life+death
Chaos:all affinities combined, chaos came before order and to chaos shall order return
*Void:the opposite of Chaos, it's before and after, nothingness.
Feasibly you could get any combination of the base affinities but these are the most common combinations as they make some sense, but darkfire, water fire, fire water, icy fire, etc. are not unheard of.
Actually dark and fire combinations are quite common among demons.
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Weapons affinities
Sword
Spear
War Axe
Dagger
War Hammer
Morningstar
Bow
Hidden weapon
Poison sac
Close combat(body)
Staff
War Fan
Lance
Whip
Boomerang
Knife
Small weapon
Halberd
Scythe
There are many more and they can get far more specifics for example you can have specifically the affinity for katana, or great sword, or scimitar, etc.