This is how Dark Harvest impacts the keystones Omnistone grants

Project: Omnistone is the rune League of Legends players like to look down upon. And that may not be because the rune is underperforming, but rather because it’s difficult to understand.

When a player goes into the game with Omnistone equipped, they basically decide to let the game pick which keystone is the best depending on the situation they’re in. Omnistone grants use of different keystones, giving higher priority to those that fit the player’s current course in the game.

But understanding how each of these keystones works when rolled with Omnistone isn’t an easy task, with the soul bonuses gained from Dark Harvest enhancing other granted keystones. To better understand the impact Dark Harvest has on Omnistone, let’s take a look at its soul bonuses, and how it plays in with the multipliers of other keystones.

Mathematical formulas have been provided by a Reddit user u/Jebsuwu, and confirmed by Riot Games.

Conqueror

Conqueror is likely to roll when the player and their enemies have high health, with a higher chance for melee champions. The keystone grants adaptive damage based on on-hit attacks, and provides healing when fully stacked. With Dark Harvest’s souls, the bonus adaptive force increases by 2.5% for each soul.

Bonus damage = Conqueror stack value + (Conqueror stack value x 2.5% x DH souls) x Number of Conqueror stacks

Fleet Footwork

There’s a higher possibility of Fleet Footwork rolling for champions below level nine that are low on health. Auto attacking and moving generate stacks that, when energized, restore health based on the champion’s damage, and grants a second long movement speed boost. Having Dark Harvest will increase healing by five, and give 5% more bonus energized MS for each collected soul.

Bonus MS = 20% + (20% x 2.5% x DH souls)

Lethal Tempo

A chance of Lethal Tempo gained from Omnistone is always the same, regardless of the situation in the game. It’s a keystone that gives bonus attack speed upon dealing damage, and also allows the AS cap to be broken. Each Dark Harvest soul will add an additional 5% bonus AS to the rune.

Bonus AS = Lethal Tempo’s base AS + (Lethal Tempo’s base AS x 5% x DH souls)

Press the Attack

Another rune Omnistone provides randomly is Press the Attack, a keystone that places stacks on an auto attacked target, with the third stack dealing bonus adaptive damage and exposing enemies. Dark Harvest will increase the damage of the last stack damage by a flat 10 per soul.

Electrocute

As Electrocute functions similarly to Press the Attack, stacking the target by dealing damage, and with the third stack dealing bonus adaptive damage, the influence of Dark Harvest is similar as well. One Dark Harvest soul will increase the damage dealt by the rune by five.

Hail of Blades

When low health enemies are near and a build is used revolving around AS and damage, Hail of Blades is likely to roll. This keystone provides a 110% bonus AS for three attacks after a target has been auto attacked, removing AS cap for its duration. Dark Harvest’s souls will give it even more AS, precisely 6.5% more for each collected soul.

Bonus AS = 110% x (1 + DH souls x 5%)

Predator

Predator is an active keystone that, upon activation, grants bonus MS and increases damage dealt the first time after the activation. While souls a player collects from Dark Harvest won’t give an additional increase in MS, it will add five more adaptive damage per soul.

Arcane Comet

Damaging an enemy champion with Arcane Comet will launch the comet for increased adaptive damage, decreasing its cooldown when an enemy gets hit with it. While there are no specific situations that will give Omnistone a higher chance of rolling the keystone, Dark Harvest’s souls will increase the adaptive damage by five each.

Phase Rush

More complicated math hides behind Phase Rush, a keystone that gives MS boost as well as slow resistance when three of its stacks are applied to an enemy. However, boost from Dark Harvest’s souls won’t increase the slow resistance, only the MS by 5%.

MS increase = [Base MS x (1 + PR bonus + (PR bonus x DH stacks x 5%)) x (1 – (Slow % – (Slow % x (75% + 75% x 5% x DH souls)]

Note that these multipliers change when MS is above 415 as a soft cap.

Summon Aery

If a champion picked has either shielding or healing power and finds itself close to an ally with low health, Summon Aery will have a greater possibility of rolling from Omnistone. Not only does Aery deal damage when it dashes to enemies, but it also buffs heals and shields. A soul of Dark Harvest will increase either damage or the shield by five per stack.

Aftershock

Aftershock provides players with bonus armor and magic resistance when they immobilize an enemy, also dealing magic damage to nearby targets after its duration. If Dark Harvest souls have been previously collected, each will add 2.5% more resistance, and 3.75 more flat damage to the shockwave.

Base resist bonus = 35 + (35 x 2.5% x DH souls)
Bonus resist from items = Resist from items x [80% + (80% x 2.5% x DH souls)]

Grasp of the Undying

Entering combat with Grasp of the Undying generates stacks, with the forth stack giving the next auto attack bonus magic damage based on champion’s health, as well as health restoration, and permanent health increase. The rune will gain an additional 3.33% healing and bonus damage per empowered attack, with a 5% increase in maximum health.

Bonus damage (melee) = Total HP x [4% + (4% x 3.33% x DH souls)
Bonus damage (ranged) = Total Hp x [2.4% + (2.4% x 3.33% x DH souls)
Healing (melee) = Total HP x [2% + (2% x 3.33% x DH souls)
Healing (ranged) = Total HP x [1.2% + (1.2% x 3.33% x DH souls)
Total bonus HP = Grasp of the Undying damage x [5 + (5 x 5% x DH souls)

Glacial Augment

If a player has an active item that slows enemies, Glacial Augment has a higher possibility of rolling. Not only does the rune give slow on auto attacks, but it also slows nearby targets when a slowing item is used. With each Dark Harvest soul, the slow effectiveness increases by 2.5%

Slow effectiveness = Enemy raw MS x  [1- (Base value x 2.5% x DH stacks)]