The frozen key is used to open the frozen door in the God Wars Dungeon. Behind the door is the Ancient Prison, containing Zaros' followers and their leader, Nex. The key is combined from four parts, each one dropped by a combatant of the other four gods within their respective camps in the God Wars Dungeon. Combatants fighting in the main central area do not drop a key piece. This makes level 70 Strength, Agility, Ranged, and Constitution necessary to obtain the key. None of the stats can be boosted. Completion of The Dig Site quest is also required for putting the key together.
Once created, the key has 10 charges, and it can hold up to 100. A charge will be used each time the frozen door is opened, and the key will end up in a degraded state once all charges have been used. The key can be repaired by Bob in Lumbridge for a cost based on the Smithing level. The cost of repairing one charge varies from 49,200 coins at level 1 Smithing to 10,000 coins at level 99 Smithing, with 400 coins saved per Smithing level. Players can also repair it on an armour stand in a player-owned house, where the cost will work in exactly the same way.
Upon destroying the key, new pieces can be gathered and assembled into a new one with 10 charges.
The frozen key pieces are dropped by any follower within each god's camp inside the God Wars Dungeon. There are four frozen key pieces, one for Armadyl, Bandos, Saradomin, and Zamorak. If all four pieces are combined they will become a frozen key, which can be used to open the door to the Ancient Prison. It is not possible to have more than one of each of these pieces at a time.
The frozen key pieces do not always trigger a loot beam and do not show up in area loot, so players should be careful to manually check their drops if they are attempting to obtain them. However, they will show up as a stack pop-up and when a monster drops its loot and show up in area loot.
During the Wild Weekends: Double Drops (19–21 May 2012) and Winter Weekends: Double Drops (1-3 December 2012), all the keys could be found in duplicate, but you could only pick one, making the other useless.