Oh boy, lol. The ring of sauron drops from witchkings and the nazgul on the surface. For the elemental crystals, I always just go to where you can find them, (corruption, underworld, ocean, space) pop a battle potion and sit near a water candle to get them to spawn. The jewels that summon OP junior and OP senior are dropped by a phantom eye that spawns in the cavern level of the world. He will only drop the jewel of the depths, which summons Ultima Weapon. But if you defeat Ultima Weapon, he'll drop the jewel that sumons Omega Weapon, and yes, all of the sword weapons drop from Ultima Weapon. Now, last question, there are alot of good mage weapons in this mod, most of which drop from Ultima Weapon (Bolt 4, Fire 4, Ice 4, Flare tome etc.) For ranged weapons, idk. I've always used the pulse tsunami from the tremor mod, which is a stupendous weapon, but as far as Omnir's mod goes, the Artemis bow is a good choice and it drops from Ultima (I think)