White Skull Edit
With the legacy mode update the skull has been reverted back to its pre-EOC mechanics.
The skull is caused by initiating combat with another player or their familiar in the Wilderness, by entering the Abyss, or by looting from a Wilderness Warband camp. Upon leaving the location that caused the skull effect, a timer starts after which the effect will be removed. This timer is 10 minutes for looting a Warband camp or entering the Abyss, and 20 minutes for initiating combat with another player. Retaliating in the Wilderness does not result in a skull. If a player dies while Skulled (and outside of a safe minigame), they will lose all of the items they are carrying as opposed to keeping the three most valuable; they will also become un-skulled. Skulled players will still leave a gravestone with all of their items if they die in an area where gravestones would normally dropped. Assuming a player is not in a high-risk wilderness world, they can still protect their two most expensive item using the protect item prayer/curse and a portent/sign of item protection.
Additionally, a player can prevent themselves from being skulled when entering the Abyss through the use of a Forinthry brace.
The Red skull is a status effect which players will gain after winning a round of the TzHaar Fight Pits. The red skull does not appear outside the Fight Pits, and disappears if the player with it leaves the Fight Pits or switches worlds. It will also disappear if another player wins the next round of the Fight Pits. Players with a red skull will not lose their items if they die, as the Fight Pits is a "safe" minigame. The only way to have the red skull outside the fight pits is with a glitch.
Pre-Legacy Update Skull Mechanics Edit
The Skull was a status effect indicated the user has Multi-way combat activated in the wilderness. The Skull will disappear after the player has left the Wilderness.
Skulled players could only engage other skulled players in combat, and non-skulled players could only engage other non-skulled players.
- In RuneScape Classic, getting marked with a skull was officially known as setting one's alignment to Evil. 
- In RuneScape 2, the skull was said to be the mark of Zamorak during the Abyss miniquest.
- Sir Renitee used to ask for the player to be skulled for switching to the "Skull" family crest.
- Prior to the legacy update the skull signified whether a player was in multi or single way combat, this has since been reverted to the pre-eoc mechanics which bases combat type based on location