Shadow Rush

The Old School RuneScape Wiki also has an article on: osrsw:Shadow Rush

Shadow Rush
Release date	18 April 2005 (Update)
Members	Yes
Level	52
Spellbook	Ancient
Type	Combat
Element	Earth
Damage	499
Runes	13
Quest	Desert Treasure
Cooldown	2 seconds
Description	A powerful earth spell, which also reduces the target's damage dealt by 5% for 10 seconds.
Infobox • Talk page

Shadow Rush is the weakest of the shadow spells. This spell requires a Magic level of 52 to cast and can reduce your target's damage dealt by 5% for 10 seconds. It has a 100% chance to reduce your target's damage when cast as an auto-attack. If this spell is used with an ability, it only has a 10% chance to reduce damage, or a 20% chance if the caster has Dark Form active. It requires a death rune and three earth runes to cast. The base damage of this spell is 499, and it scales up to 604 at 63 Magic.

As with all Ancient Magicks spells, the quest Desert Treasure is required in order to cast this spell.

Cost

Input	Cost
31	293
Combo runes
13	3,293
13	2,786
13	3,173
Staves
1	236
1	236
1	236
1	236
1	236