Desert strykewyrms are a Slayer monster that require a Slayer level of 77 to kill. They are found burrowing in the sands west of the Abbey of St. Elspeth Citharede, and stomping on the mounds will cause a strykewyrm to appear if you have been assigned to kill them. Strykewyrms are intelligent and sense whether a player is intent on fighting them, so they will only appear if this is the case.
Once revealed they will stay in the exact spot they spawned at unless performing their special attack. This attack consists of them disappearing under the sand and then springing up under you and dealing 500-1000 life points of damage. To counter this special attack you must run away at least 2 squares away from your original position. Their melee attacks are far more accurate than their ranged strikes, so ensure you use high-level armour or bring enough food.
These beasts are a good Slayer task as they offer nice Slayer experience and also a decent amount of money; you may average as much as 500k profit per task. Notable drops include large amounts of pure essence, potato cactus, death runes, etc.; however if you are lucky you may receive a focus sight as a rare drop.