Ice strykewyrms are the strongest species of strykewyrm, requiring a Slayer level of 93 and completion of The Tale of the Muspah to kill, as they are only found in a chamber of the Muspah Cave. Strykewyrms are intelligent and will only confront players who are intent on killing them, therefore you must be on a Slayer assignment of ice strykewyrms to face them.
Ice strykewyrms are weak against fire magic, and using it will give a damage bonus. If you are using the ancient spellbook, Bloodfire Blitz will prove to be a devastating weapon when used alongside combat abilities (the Bloodfire Barrage spell has the same base damage and uses more runes so there is no reason to use it.)
Ice strykewyrms normally use melee attacks with occasional magic, but they can also burrow beneath their attacker and burst out of the ground. This attack can deal 1000+ damage so watch the strykewyrm closely and move at least 2 squares away when it burrows.