The archers ring is one of the Fremennik rings and is dropped by the Dagannoth Supreme in the Waterbirth Island Dungeon. The Fremennik rings are some of the very few rings in Arigon to give stat bonuses, and the Archers' ring is considered to be the best ring for rangers to use.
It can be enchanted into a Archers' ring (i) Archers' ring (i) by using a Ring of scrolls, obtainable from the Slayer Rewards