Law staff

The Law staff is a magic weapon, released with the Dungeoneering update, on 12 April 2010. It costs 10,000 Dungeoneering tokens and requires level 45 Dungeoneering and 45 Magic to acquire and wield. Players can store up to 1000 law runes within it, and when used it has a 1/10 (10%) chance of not using a law rune.

Although it may seem as though the law staff's ability would save the player more money due to law runes being more expensive, the fact that there is only a 10% chance of saving a rune means that the monetary savings after 10 teleports only amount to coins (the price of one law rune). With a staff of air or similar staff which provides unlimited air runes, the savings for the same 10 teleports amount to after preserving 30 runes, proving much less costly in the long run.

Cost analysis
The following is a comparison of the cost per cast of spells using Law runes while using an elemental staff as opposed to using a Law staff. The cost per cast when using the Law staff is approximate and assumes that exactly 1 out of 10 Law runes are saved.

Standard spells
Example on reading the table:
 * The cost of Varrock teleport using a Fire staff is 0 gold.
 * The cost of Varrock teleport using a Law staff is 0 gold.

Trivia

 * The law staff used to cost 60,000 Dungeoneering tokens before the 21 April 2010 update.
 * The law staff can be used for teletab creating, and the 1/10 chance to save runes is still there.