Incredible Reflexes is a prayer unlocked in the standard prayer book once level 34 prayer is achieved.
Incredible Reflexes increases the user's attack level by 15% when in use. The maximum bonus with Incredible Reflexes is 15 attack levels, once the user has reached an Attack level of 99 (0.15 * 99 = 15). This can effectively boost attack to 114, the highest for free-to-play players.
Use In PvP
Incredible Reflexes is extremely common in PvP situations, most commonly the Wilderness. It is often paired with Ultimate Strength and Steel Skin. This combination of prayers can boost Strength, Attack, and Defense to 114.
Incredible Reflexes drains prayer points at a rate of 200 points for every minute passed. With 99 prayer, Incredible Reflexes can be sustained for 5 minutes when used by itself. This is often enough to last a PvP fight, which typically last from 1 to 3 minutes long.