If players wear an unholy symbol while in the waiting room of Saradomin in Castle Wars, they will be transformed into a rabbit. If players enter the Guthix portal wearing an unholy symbol, they will turn into sheep until the start of the next game.
When the item was first released, it was not tradeable.
Before an update it used to be made from gold instead of silver. Again, after a hidden update, the symbol's colour was changed to silver. After yet another update, they are currently made from silver, but the symbol is gold in colour with an unknown grey piece accompanying it.
If players wear an unholy symbol in the God Wars Dungeon it will count as Zamorak equipment and faction monsters will no longer be aggressive to them.