The Eye of the Herald is a neutral buff dopped by the Rift Herald when it dies. It is available only on Summoner's Rift. Only members of the team that killed the Rift Herald can pick it up. If nobody picks it up it disappears after 40 seconds.
The Eye of the Herald replaces the trinket item in your trinket slot. You can break the Eye to summon Rift Herald to aid your team.
Enemies hear an audio cue when the Rift Herald is summoned.
While there are no allies nearby, you take 5% damage reduction from enemy champions and generate X / Y (based on level) Corruption stacks per second. At 100 stacks, your next basic attack consumes all stacks to deal 15 / 270 (based on level) bonus magic damage. Works versus structures, damage halved for ranged champions.
Lasts for 20 minutes and is retained even if slain.