Warped Armor:Rift Herald's is immune to all disabling debuffs.
The Eye of Baron: After being in combat for three seconds, the eye on Rift Herald's back will open. Champion basic attacks against the eye deal (12% of Rift Herald'smaximum health)bonustrue damage, causing the eye to close for 10 seconds, reduced by 2.5 seconds every time she is struck by a champion's basic attack.
Rift Herald's has a couple of special moves:
Charge: At the start of the fight, Rift Herald winds up and charges forward, knocking aside enemies she passes through and damaging them for 200% AD.
Swipe: At certain health thresholds, Rift Herald winds up for an attack that deals 300% AD in a cone in front of her.
The Eye of the Herald, once collected, replaces the Trinket of its owner. Activating the Eye will crush it, starting a 3.5-second channel that, upon completion, summons the Rift Herald to push the respective lane. If the channel is interrupted, the Eye will be lost and the Rift Herald won't be summoned.
In lane, the Rift Herald relentlessly pushes her way to the Nexus. With a hefty amount of HP and damage, plus a variety of skills focused on taking down towers, the Rift Herald can rapidly destroy multiple towers if left unchecked. Since the Rift Herald prioritizes minions and structures, it is not possible to distract her from smashing your towers - the only way to stop the Rift Herald is to take her down.
Thankfully, the Rift Herald is not as durable as it was in the pit, and there are a couple of natural methods to whittle down her HP:
The Rift Herald loses HP over time, and loses HP when she headbutts towers, but not inhibitors or the nexus.
Every 3 seconds, the eye on Rift Herald's back will open. Champion basic attacks against the eye deal (20% of Rift Herald'smaximum health)bonustrue damage.
Rift Herald will dance if a champion dances nearby, or if she is alive and near the enemy Nexus when it is destroyed.
Rift Herald's charge attacks against towers or other structures can be blocked by Champions if they stand between the Rift Herald and the attacked structure. This causes the charge attack to deal very little damage against the initial target but instead damages the blocking champion.
If the Rift Herald is in range of two structures and winds up to charge at a structure that gets destroyed before she starts to charge, she will charge to the next available structure instead from the same wind-up. 
In patch V7.9, it was stated that Rift Heralds were exclusively female.
From patch V5.22 to patch V7.9, the Rift Herald looked like this:
Bug Fix: Fixed a bug where canceling Eye of the Herald's summoning ritual at the very end of its 0.25 seconds wind-up (before the uncancellable 3-second channel begins) could cause the item to go on an extremely long cooldown, preventing it from being used before it expires.
New Effect: Rift Herald is captured in the Eye of the Herald when killed. Any member of the team that killed Rift Herald can pick it up, temporarily replacing their trinket. Eye of the Herald grants Empowered Recall while held and expires after 4 minutes if not used. Channeling Eye of the Herald for 3.5 seconds will crush it to summon Rift Herald from the void as your team's ally.
Has 4000 - 6400 health, 425 movement speed, 80 - 200 attack damage.
Basic attacks deal 3% of Herald's current healthbonus damage, in addition to base AD.
When Rift Herald approaches turrets she winds up and leaps into melee range, dealing 150 damage (+ 25% of her current health) to the turret and herself.
Eye opens every 3 seconds.
Poking Rift Herald's eye deals 20% of her maximum health as damage.
Rift Herald can be affected by most forms of crowd control.
Rift Herald disables turret backdoor defenses even when no allied minions are nearby.
While there are no allies nearby, you take 5% damage reduction from enemy champions and generate X / Y Corruption stacks per second. At 100 stacks, your next basic attack consumes all stacks to deal 15 / 270 bonus magic damage. Works versus structures, damage halved for ranged champions.
Lasts for 20 minutes and is retained even if slain.