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.
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.
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.
Active:Hecarim gains 75% movement speed over the course of 3 seconds, starting with initial 25% upon cast, and ending one second afterward.
While Hecarim is charging, he gains 150 extra attack range (325 total). His next attack knocks back the target, dealing physical damage based on how far Hecarim has traveled during Devastating Charge's duration.
Active:Hecarim summons spectral riders and charges forward with them in a line, dealing magic damage to enemies in their path.
Magic damage: 150 / 250 / 350 (+ 100% AP)
Enemies within range of where Hecarim stops will flee in terror for 1 second.
The wave of spectral riders will travel the maximum distance possible in the direction of the cast, regardless of where Hecarim himself stops.
Щиты от умений: 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.