Buy RS3 Moonstone necklace
The Moonstone necklace is a members-only piece of moonstone jewellery in RuneScape 3. It goes in the neck slot and has no combat stat requirements. On its own it is purely cosmetic, so it gives no damage, accuracy, or armour bonuses. It is light at 0.01 kg, and it is tradeable and noteable.
The real value comes from enchanting it. With level 68 Magic and the Lvl-5 Enchant spell, the necklace becomes an alteration necklace. This enchanted version boosts the power of alteration glyphs by 20% during Necromancy rituals, which makes it a strong pick for Necromancy training. A Lvl-5 enchant tablet can also be used with no level requirement.
Crafting one yourself takes work. You need level 77 Crafting, a furnace, a necklace mould, a moonstone, and an ensouled bar. Ensouled bars are untradeable, so you also need level 60 Necromancy to make one, or you can buy one from Thalmund's Wares. You must first learn to craft moonstone jewellery from the Former Master Crafter in the City of Um by completing the Mystical Moonstone achievement. Buying the necklace ready-made lets you skip all of those steps.