The Primeval robe top is a level 90 Magic tank torso slot item, part of the Primeval equipment set. It can be purchased for 12500 Teci (rewarded for completing Raids) from the Armoursmith in Mazcab. Besides Daemonheim-only armour, it offers the best defensive bonuses for any item in its slot, tied with other Raids equipment.
The primeval robe top degrades to dust after 100,000 charges of combat, and cannot be repaired. Fighting in Raids does not degrade it at all. When wearing the full regular or Achto Primeval set, or a mix of the two, there is a 2% chance per piece that all of your defensive abilities will have their cooldowns reset. When this happens, there is a 1 minute cooldown before they can be reset again. Owning the primeval robe top also doubles the chance of getting the Achto Primeval robe top as a drop from one of the Raids bosses. If you die in the Wilderness with the primeval robe top, it will drop 6 million coins instead of the item.