Obsidian platebody

The Obsidian platebody is part of the untradeable and degradeable Obsidian armour set. It requires 80 Defence to wear, and can be made by smithing five obsidian bars, requiring 90 Smithing. Obsidian bars are made by smelting obsidian shards, which in turn are dropped by monsters in the Fight Cauldron.

In addition to its defensive bonuses (equal to the torva platebody), it provides 5% reduction in damage from creatures in and around TzHaar City. However, it is only useful when fighting TzHaar and TokHaar -- outside that area, and in PvP, the obsidian armour will triple damage towards you.

When used with the rest of the obsidian armour and either an melee, ranged or magic helmet, it will increase your accuracy by 10%, very similar to the Void Knight equipment.

The Obsidian platebody degrades after 3000 hits, similar to the Tokkul-zo. Once it fully degrades it cannot be reused, and a new platebody must be smithed.

Trivia
While the concept art shows a bulkier left portion of the shoulder and arm plating, the ingame model has quite slim plates on the armor's left portion. This is likely due to graphical issues as the bulky arm would stick through shields and get in the way of many animations.