Agro is a very loyal horse to Wander, and it is quickly apparent that the two have been together for a long time. After each colossus is slain, Wander awakens in the central Shrine where Agro is seen galloping in a few seconds later. Agro's speed aids Wander in many battles, either by keeping him from harm (versus Basaran and Dirge) or by allowing him to catch up with a fast-moving enemy (Phalanx).
Before the final colossus, Wander must cross a collapsing bridge that he cannot cross quickly enough on his own. He runs across with Agro but, even she falls short just before the end. Agro bucks Wander to safety and falls into the chasm below while Wander watches helplessly. The young man is subsequently forced to finish his quest bereaved of his last living companion.
In the game's epilogue after Dormin and Wander have been consumed by the whirlwind and Mono reawakens within the Shrine, Agro is revealed to be alive, albeit having suffered injury to her hind leg, limping heavily as a result. It is not clear whether Mono recognizes the horse, but she follows her to the stone basin at the back of the Shrine - revealing the horned infant Wander - and onward to the mysterious garden above.
There has been a lot of confusion and debate regarding Agro's gender. Fortunately, Fumito Ueda has confirmed Agro's gender as "a girl" in an interview in the official artbook and guidebook. Many fans still believe Agro is a stallion, due to the mistranslation (where Agro is referred to as male) in a tutorial message.
Agro has a diamond-shaped patch of white fur on her head between her eyes. If there is a save file from Ico on the same memory card when a new game is created, Agro will have an "I"-shaped patch on her head from the Ico logo instead. Unfortunately, there is no way to "upgrade" the marking on Agro to an Ico symbol after a game has been started and saved; the only way to get the "I" marking is to start a brand new game with an Ico save file. There is one exception to this: starting a session of Time Attack with an Ico save file on the same memory card will change Agro's symbol to the "I" (provided the foe is one of the five colossi Agro can make it to), but the symbol will return to the regular design once back at the Shrine of Worship.
Two different colors for Agro can also be unlocked: brown and white. To unlock Brown Agro, all 16 challenges in Time Attack must be cleared. For White Agro, every challenge in Time Attack on both Normal and Hard must be conquered. The player will be notified when they have successfully unlocked both Agro colors, as well as how to access them; to change to Brown Agro (or from brown back to default), hold down at the title screen while selecting Load Game. To change to White Agro (or from white back to default), hold down at the title screen while selecting Load Game.
In addition to its standard release, BluePoint's 2018 remake for Shadow of the Colossus was also released as a special edition which included the "spotted steed" Agro skin and two new items, the Ancient Bow and the Cloak of Fate. This new skin is a brown and white tobiano (see gallery).
The 2018 remake also modified the white diamond on Agro's forehead, making it a whorl instead of a patch. This whorl is present on her original "black" coat, but is absent from the "brown" and "white" skins. The "crested" Agro skin looks much like her original black, save that it has gray feathering, and the whorl has been changed to be a downward-facing Ico horn. The whorl on the "spotted steed" skin has also been changed from the whorl; it is a large patch that originates at the forehead and spans to below the eyes, reaching halfway down the face. The original whorl of the "black" skin looks reminiscent of the whirling clouds above the pillars of light that form over each fallen colossus.
- Though no theme plays for Agro in-game, the track "Swift Horse" will play following the end credits when unlocked modes and features are revealed for subsequent playthroughs.
- Given that she can run at full speed for large distances, Agro is most likely a thoroughbred horse, built for endurance rather than bursts of short speed. The only confounding factor of this theory is that when measured against the colossi and Wander, she is as tall as real-life draft (heavy) horses.
- Agro's top speed is somewhere between 40 and 50 mph.
- If Wander points his bow and arrow at Agro, she will rear up and neigh before galloping away and out of the line of fire. Strangely however, she won't react when hit with the sword, which makes a metallic noise when it strikes her.
- Agro will stop if she comes to a drop that is too big to jump, turn and steer around objects by herself whilst Wander rides her, and will slow down if she is traveling across, for example, a narrow path (such as the natural bridge that leads to Kuromori's lair).
- Agro can be injured by any of the colossi that she has access to (Quadratus, Phaedra, Basaran, Dirge, and Phalanx). When she is damaged, she will hobble briefly before returning to normal with no apparent permanent or long-lasting damage.
- There is a glitch with Agro where if Wander defeats all 16 colossi in Normal Time Attack, collect all the items, and then die before saving the game, the player won't have any items they had after the last time the game was saved. The colossi must be defeated again to get the items back. If these criteria are met, brown and white Agro will both be available in Normal mode.
- Although many fans believe that Agro suffered a broken leg at the end of the game, it is much more plausible to say that it was only severely sprained, because if the actual bone was broken, the resulting pain would have certainly prevented her from swimming to shore and limping all the way back to the shrine.
- If left alone for a decent amount of time, Agro may wander off to graze or drink nearby. A good example can occur after Wander wakes up following the defeat of any colossus; if Wander does not immediately ride out of the Shrine, Agro will walk into the field nearby to graze. If Wander continues to let her move about, Agro will turn back and reenter the Shrine, coming to stand right beside the altar as she does in the cinematic following the fourth colossus. Although not difficult to trigger, this event requires keeping a good distance from Agro as she may think Wander wishes to mount and will stop roaming.
|Characters||Wander · Mono · Agro · Dormin · Lord Emon · Guards · Shadow Creatures|
|Colossi||I · II · III · IV · V · VI · VII · VIII · IX · X · XI · XII · XIII · XIV · XV · XVI|
|Locations||The Forbidden Lands · Shrine of Worship · Colossi Arenas|
|Main Items||Power-ups (Lizards · Fruit) · Weapons (Ancient Sword · Sword of the Sun · Queen’s Sword · Sword of Dormin · Bow & Arrow · Ancient Bow · Harpoon of Thunder · Life Sword) · Collectibles (Relics)|
|Gameplay||Hard Mode · Save shrines · Time Attack · Reminiscence Mode · Watermellon · Barrel|
|Media||Roar of the Earth (OST) · Official Art and Guide Book · Nico Bonus DVD · Film|
|Releases||Demo · PS2 original · PS3 remaster · PS4 remake · Credits|
|Unused Content||Beta Mountains · Unused Colossi · Sluice|