Wild thought to start with: I’ve dug through the gear lists and my own bank a dozen times, and there isn’t a canonical ‘celestial ring’ in 'Old School RuneScape' that you can obtain like a normal in-game item. Players sometimes toss around names from other versions of the game or from fan-made content, so that’s where confusion usually starts.
If you’re hunting something that sounds celestial — like a ring with magical or cosmetic flair — the usual OSRS routes apply: check the Grand Exchange for similarly named items, grind boss/raid drops, finish clue scrolls for unique rewards, or keep an eye on seasonal events and holiday promos that sometimes hand out one-off cosmetics. For functional rings, most come from boss drops, clue rewards, or are crafted/enchanted with Magic and Crafting requirements. Personally, when I thought I’d missed an item, the wiki and GE search cleared it up fast; saved me from chasing a phantom ring and let me focus on real targets instead.