A Toktz-ket-xil, roughly translated to "sharp obsidian defender", is an obsidian shield that requires level 60 Defence to wield. It cannot be made using any skills.
The price of the obsidian shield has fallen dramatically to near its high alchemy value. This made the obsidian shield a good item to high alchemise, due to gaining profit out of it at times.
Before the Evolution of Combat, some players speculated that this was the equivalent of a dragon kiteshield at its time, having a 60 Defence requirement and being red with black spikes.
In the 46th Postbag from the Hedge, TzHaar-Mej-Tak mentions that an obsidian shield is used in a similar way to a defender, rather than a shield. This explained its former strength bonus.
While wearing warpriest of Zamorak armour, equipping the shield causes a brightness effect on the cap, causing it to appear much brighter than before, appearing charcoal grey instead of black.