Hecarim has no unit collision of his own, and does not block other units' pathing. Potentially, this can have the dubious effect of allowing him to completely obscure the click area of a minion or smaller allied champion with his large hitbox.
The amount of bonus attack damage granted is checked every 0.25 seconds
COST: 32 / 34 / 36 / 38 / 40 Mana
Active:Hecarim cleaves nearby enemies, dealing physical damage that is increased by 50% against monsters and champions.
Rampage has no cast time and does not interrupt Hecarim's previous orders.
Rampage stacks reduce the ability's base cooldown, distinct from the usual flat cooldown reduction of abilities such as Undertow and Arcane Mastery. This means cooldown reduction from items, runes or masteries is applied after the reduction from any Rampage stacks. This makes Rampage's minimum cooldown 1.2 seconds at 40% cooldown reduction and 2 Rampage stacks, instead of 0.4 seconds. (There is a bug known as of patch 5.22 where the Q is not reducing the base cooldown by 2 seconds and is reducing the total cooldown by 2 seconds. This means rampage has a theoretical cooldown of .2 seconds with 45% CDR.) The discovery of this bug is given credit to the popular streamer Sickmotion.
Spirit of Dread
COST: 50 / 60 / 70 / 80 / 90 Mana
COOLDOWN: 22 / 21 / 20 / 19 / 18
Active:Hecarim surrounds himself with the spirit of dread for 4 seconds, dealing magic damage per second to all enemies within its reach.
The sole exception to this is for abilities that cost health - Hecarim will not heal if an enemy expends health to cast a spell within Spirit of Dread's radius.
Spirit of Dread's minion healing cap is based on total healing from all minions. This means that Hecarim can only be healed for up to 60 / 90 / 120 / 150 / 180 health regardless of how many minions are affected by the spell.
COST: 60 Mana
COOLDOWN: 24 / 22 / 20 / 18 / 16
Active:Hecarim gains bonus movement speed for 4 seconds, beginning at 25% and increasing to 75% over 3 seconds.
While Hecarim is charging, his next basic attack gains range, knocks back his target, and deals physical damage based on how far Hecarim traveled during Devastating Charge's duration, ending its effects in the process.
Devastating Charge has no cast time and does not interrupt Hecarim's previous orders.
Devastating Charge resets Hecarim's autoattack timer on cast.
Devastating Charge's cooldown begins on cast, not when the buff expires.
The percentage movement speed bonuses provided by Devastating Charge are applied additively.
For example, the ability in tandem with a Trinity Force, Ghost and no other modifiers will result in a net movement speed modifier of 8% + 27% + 175% = 210%.
Onslaught of Shadows
COST: 100 Mana
COOLDOWN: 140 / 120 / 100
Active:Hecarim summons spectral riders and dashes forth with them in a line, becoming immune to crowd control while charging and dealing magic damage to all enemies in their path. Enemies within range of where Hecarim stops also flee from him for 1 second.
Magic damage: 150 / 250 / 350 (+ 100% AP)
The wave of spectral riders travels through Onslaught of Shadows's full length, regardless of where Hecarim himself stops.
Spell shields will block the fear, but do not block the riders' damage.
Onslaught of Shadows' flee will only be applied to enemies near Hecarim when he finishes his charge. It is not applied to enemies that are only hit by the riders. This is not conversely true - enemies who are feared by Hecarim will always receive the damage as well.
Onslaught of Shadows' flee is distinct from the usual fear in that affected units will always travel away from Hecarim for its duration, and it has a different Loss of Control Indicator icon to show this. The flee is dynamic, meaning that the affected target will continue running away from Hecarim, even as he continues to move himself, allowing some degree of control over where affected units will run.