To cast the spell, the player must be wielding Iban's staff; thus, the player must complete Underground Pass in order to be able to cast the spell. Each cast consumes one charge from Iban's staff when cast on an NPC, or two charges if cast on another player. Thus this spell can be cast a total of 120 times (60 in PvP) before the staff must be recharged (2500 (1250) with Iban's upgraded staff).
As of 21 August 2014, Iban's Staff can be used to auto-cast Iban Blast.
Note that because Iban's staff is required to cast this spell, the player cannot use elemental staves to substitute any of the runes. A Tome of fire can be used, however, and will not consume any of the tome's charges.