The Jeweled Signet of Melandrus is an item that drops from Court of Stars, a Legion dungeon. This ring was very powerful for melee classes as it gave 10% bonus damage to auto-attacks. Since Legion ended, Blizzard added a tag to the effect, preventing it from being used for characters level 50 or above. However, with Patch 9.1.5, this effect has been reworked but now works at max level!
This flat value now also scales with item level which means that during Legion Timewalking, melee classes may want to pick up this ring and upgrade it using Valor to scale the flat value as high as possible. It scales to 13 damage at item level 184, and scales to +36 at item level 246 (the highest Valor item level).