[Legolas]

As you probably know, it's no use trying to talk him out of the fight.

I think I would first try to distract him with a summon and slip a Harm spell through his spell resistance (use (improved) combat casting to prevent attacks of opportunity). Follow that up with a good hit or other damage spell while he uses his three cure critical wounds potions or repeat as needed, and you'd be through.

Of course, he does have SR 32 so if your feats don't lean towards spell penetration it might be hard to pull off.

Your other option is to fight him. I might be off a little bit but you're facing about six attacks per round with an attack bonus of 33, and you have to knock off 241 hitpoints through an AC of 43.
I'm not sure what your own combat feats, items and domains are, but with Haste and a Barkskin potion any cleric of your level should be able to get to an AC of 45, four attacks per round and an ab of 39 using basic full plate, a tower shield and random weapon.

If you have protective items giving a +6 AC bonus or better, any AC on your boots, or an AC amulet of over +3 you can boost your armour class further, just as with (improved) expertise, Armor Skin or Divine Shield feats. Get it up to 53 and he'll only score about one hit every three rounds and drastically reduce the critical hits he scores (he's a fighter/weapon master)
If you have weapon feats or a weapon of +6 or better enhancement, your ab likewise goes up. You should be hitting once per round. Sadly though, he's immune to critical hits and sneak attacks.

You might also try to disarm him if you have the feat. He does have good discipline but he'll be a lot less dangerous without his two-bladed sword. It's also the sword that gives him a 10/- electrical damage resistance, though that would make little difference.