You are unable to speak to the Mage of Zamorak at the Chaos altar if you are wielding or wearing an item representing another god. He will tell you not to wear such unholy things in such a holy place.
During the Wanted! quest, you need to pay the Mage of Zamorak 20 unnoted rune OR pure essence in exchange for information.
The Mage of Zamorak's Battle Runes store sells:
|Fire runes||Water runes||Air runes||Earth runes|
|Blood runes||Mind runes||Chaos runes||Death runes|