Discipline, Holy:
Launch a Holy bolt that grows in power with distance, healing an ally for up to (54% of Spell power), and then bouncing to additional allies 4 times. Each time it bounces, it splits into 2 bolts.
Shadow: Launch a Shadowy bolt that grows in power with distance, damaging an enemy for up to (183.6% of Spell power), and then bouncing to additional enemies 4 times. Each time it bounces, it splits into 2 bolts, never damaging the same target twice.
Cascade's effect depends on the priest's target. If the target is friendly, the spell will bounce from ally to ally, causing healing; if the target is not, the spell will bounce from enemy to enemy, causing damage. It is possible to self-cast Cascade. Unlike most AoE spells, this spell will not deal damage to non-aggroed mobs, regardless of range, making it safe to use even in crowded situations.
Cascade does between 40% and 100% of its max damage/healing based on the linear distance between the source and target of the bounce. It does 40% of its maximum damage at 0 yards, and 100% at 30+ yards, scaling linearly between those two points; anywhere between 30 yards and 40 yards will give 100%. It prefers farther away targets when it bounces.[1]
Cascade jumps up to 4 times, affecting a potential 31 targets.
Cascade will not bounce from targets that are killed by its effect. When choosing a hostile target, players should therefore take care to select one that is likely to survive Cascade's effects, ensuring at least one bounce.
Because Cascade's effectiveness is significantly determined by distance, priests should generally cast it on a target that is at least 30 yards away whenever possible. From there, Cascade will prefer to bounce to distant targets (within 40 yards), maximising its effect. In contrast, self-casting guarantees the first effect will only grant 40% of its potential healing.
Unlike the other level 90 priest talents, Cascade only provides damage or healing. Cascade is also the only of the talents whose effect is determined by target. Cascade could be considered the least sensitive and precise of these talents, since its effectiveness is only minimally determined by the priest's position and choice of initial target. In contrast to the other talents' functionalities, Cascade's 40 yard range also makes it possible to use it at full effectiveness from a substantial distance, making it easier for priests to stay out of the fray. The initial bounce aside, Cascade's target-to-target pattern also less obviously signposts the priest's position than the other talents' effects.
Hotfix (2015-07-07):Cascade now deals 20% less damage in PvP combat.
Patch 6.1.0 (2015-02-24): Cascade may now hit the same target twice. This results in an increase to total healing, so its healing has been reduced by 35% to compensate (the total healing in a 20-player raid will be slightly higher than before).
Discipline and Holy: Cascade now has a 1.5-second cast time (up from instant cast, see also: instant cast heals), heals for 50% less, and no longer damages enemies.
Shadow: Cascade no longer heals allies.
Hotfix (2013-09-17):Cascade should no longer hit PvP enabled players if the Priest is not PvP enabled.
Patch 5.4.0 (2013-09-10): Effect can now bounce up to 4 times (up from 3), and its effect should no longer bounce between minor guardians (Wild Imps, Bloodworms, Snakes from Snake Traps, etc.).
Hotfix (2012-10-12):Cascade now deals 25% more damage or healing.
[Chakra: Sanctuary]'s aoe healing bonus, and when 
[Chakra: Serenity] is active will refresh 
[Renew] on targets.
Ghostcrawler 2012-06-20. Beta Class Balance Analysis. Blizzard Entertainment. Archived from the original on 2012-06-20.
