Icy Skeleton uses Melee-Bassed attacks and has a level of 584. But don't be alarmed, they're not aggressive, therefore you have to attack them first before they attack you.
Icy Skeleton can be found in three different locations, such as Sponsor Zone, also known as Ownercape or Ownercape Zone (you must be a sponsor), Extreme Zone (you must be an extreme donator), and by using the Boss Teleport System.
In order to kill the Icy Skeleton officially is to use a fast hitting weapon, such as a royal sicle(u),Ice katana, or a space jam. Good armor to be using is Dragonbone Melee Armor or Flame Torva. You also need to use prayer "Soulsplit" (92 prayer recommended).