Rapid Renewal is a Prayer which reduces the interval between natural healing to the user's Life points from 6 seconds to 1.2. It requires both level 65 Prayer and level 65 Dungeoneering to use. It currently has the fourth highest prayer level required for any prayer in the default prayer book. To unlock this prayer, a scroll of renewal needs to be purchased, at a one-time cost of 38,000 Dungeoneering tokens.
This prayer can be an effective way to recover life points without using food. Rapid Heal drains the prayer points of its caster by 33 points per minute. In order for Rapid Renewal to be cost-effective, it would have to drain a player's prayer by a maximum of 5/2 times the drain rate of Rapid Heal, or 82.5 points per minute. (This equation can be rewritten as [Restoration rate with Rapid Renewal on/Restoration rate with Rapid Heal on] x [drain rate of Rapid Heal])
However, Rapid Renewal drains a player's prayer points by 100points per minute. This high relative drain rate, along with the expensive cost and excessive amount of time needed to attain this prayer, brings the true merit of this prayer under question. Also note that a player will not recover life points in combat. However, if a player has access to an altar that is near where they are training, then this prayer will be very useful. Despite this, many players choose to purchase the prayer as it needed to complete the hard Daemonheim Tasks, which provides considerably useful benefits within Daemonheim, experience rewards, and 38,000 tokens upon completion (refunding the cost of the prayer). Note that completion of the third task set is also required to claim the rewards for completing the fourth task set.