Crystal strykewyrm

Crystal Strykewyrms are located directly under the grave of Glissa. You only can access them after having done The Princess and the Warrior Quest. You also need to wear a Slayer cape (requiring level 99 slayer) to get them as a task. Like with all Strykewyrms, you need to be assigned to them to kill them. They have the same drop rate for the Crown of Seren and the Amulet of Seren as the Crystal Dragon. Like all Crystal creatures, these have very high defence and can hit very accurate. High hits are 30 with melee and 40 with range. If you pray against range and range/mage them, they will come to you and fight you with close combat. There are no safespots. These are currently the only monster requirering 99 slayer to kill.