D&D clerics perform exorcisms and turn undead. That’s very D&D, as in it’s part of it’s implied setting. Other settings’ clerics should have different powers, or else what you’re really playing is your setting mixed with Blackmoor.
An easy way to do this is to replace Turn Undead with granted powers.
If you want a “Classic Greece/Swords & Sandals” approach, let clerics use spears and replace Turn Undead with the following powers, depending on the god. A priest of a given god can use their god’s granted power once a day, twice at level 3, thrice at level 6:
- Zeus’s Lightning: lightning can be called from the sky, dealing 1d6 damage on an opponent.
- Hera’s Revenge: if the cleric is wounded, the same amount of damage is dealt to the attacker. This power can be used instantly and during the opponent’s turn.
- Aphrodite’s Looks: charm person.
- Poseidon’s Spawn: a small horrible monster (2HD, ATK bite 1d6) appears and fights the enemies of the priest.
- Athena’s Wit: the priest can spend a minute coming up with a plan that can either automatically win initiative or gain surprise.
- Demeter’s Care: cure light wounds.
- Apollo’s Scrying: augury.
- Artemis’s Aim: the cleric can use a bow. One arrow shot hits automatically.
- Hephaestus’s Forge: for the rest of the combat the party’s weapons become so sharp all opponents have ac 9 .
- Ares’s Hand: after the cleric hits, the damage dealt can be doubled.
- Hermes’s Speed: the priest can outrun a group of opponents.
- Dionysus’s Wine: dance. If the subject is attacked they will stop dancing.
- Hades’s Shroud: invisibility self for 6 rounds.
- Hekate’s Keys: knock or animate dead (1 hd per caster level, maximum 2 hd per caster level controlled) or trivial knowledge (the cleric knows something useful about a topic) or find the direction (the character, in a crossroad or fork in the path or dungeon room or whatever can find what’s the right way toward a chosen destination) or poison use or light or look I have a dog (the cleric has a pet dog of 1 hd more than their level, if it dies the new pup will start at level 0 and grow appropriately at a rate of 1 level a month until it reaches cleric level +1).
Right, I cheated for Hekate. Just pick a power. Hekate’s portfolio seems to be pretty much more or less everything you ever wanted. Quoting the wikipedia:
She was variously associated with crossroads, entrance-ways, dogs, light, the moon, magic, witchcraft, knowledge of herbs and poisonous plants, ghosts, necromancy, and sorcery
More in general, this was actually not an uncommon thing. Religion in ancient Greece was not homogeneous, and gods were worshipped in many different aspects and with different rites. Also, the split between Chthonic and Olympic was not as clear-cut as we imagine it, and many European intellectuals from the Renaissance to the 19th century and the Romantics spent a lot of effort to fit the square peg of Hellenic worship practice into the round hole of a Christian perspective, including a split of “Olympians good/Chthonic and Titans evil” and much other bullshit.