At the Mounted Archery Camp in the Faron Grasslands, Link encounters a young man named Straia who is doing an ecological survey of the area. He tells Link about a wild Giant Horse in the Taobab Grasslands and asks him if he will bring it to him as mounted Bokoblins and two powerful Lynels make entering the grasslands where it is found extremely dangerous.
Link can either choose to simply avoid these enemies and head to the grasslands, either by horse or scaling the nearby cliffs or paragliding down from the Great Plateau which boarders the grasslands. Alternatively he can kill all these enemies which while more dangerous, makes the return trip much easier.
Link must then tame the horse by sneaking up on it from behind and mounting it as usual, though the Giant Horse is more warier forcing Link to crouch walk as slowly as possible. Link can increase his sneak ability by wearing clothing and using items granting stealth, to sneaking up behind it more efficiently. Once behind it, Link must them mount it and then soothe it to tame it before his stamina runs out. Due to its size and strength, it can easily drain two circles of stamina, though Link can use Energizing Elixir, Enduring Elixir, or any other items that boost or restore the Stamina Gauge.
Once properly tamed, Link must then ride the horse back to Straia. If Link took out the all enemies, the way will be easier, however the enemies confrontation will be harder as the Giant Horse has zero Spurs and thus lacks the ability to gallop. However it is still possible to get past these enemies, Link can outride them by improving the affinity bond with the Giant Horse, making it obedient to easily escape from the Lynels and mounted Bokoblin. Link can bond with it by riding it around the Taobab Grasslands area, soothing it when it follows his commands or by simply feeding it apples and any carrots. After examining it, Straia is convinced that it is a rare breed and that it is strong enough to tramp monsters. He rewards Link with a silver Rupee and allows Link to do whatever he wants with the Giant Horse afterwards.
The Giant Horse
The Giant Horse is a unique horse with five Star in Strength, though only two Stars in Speed, no stars in Stamina, and has a Wild temperament. Like Epona, its mane, bridle, and saddle cannot be changed, though unlike Epona, it can be named when registered. The Stable hand explains that its giant size prevents them from changing its bridal and saddle and that it would not like its mane being handled.
Reference and theory
The Giant Horse may be a reference to the Gerudo Stallion, the Ganondorf's Steed, since it has a reddish orange mane and dark coat, and it is found near the Gerudo Highlands, the place where Ganondorf comes from. Though unconfirmed, this Giant Horse may actually be a Gerudo Stallion itself the same breed as Ganondorf's Steed according to Gossip Stones in Ocarina of Time. Its large size, strength, and wild temperament also matches Ganondorf's character as he embodies those traits and would likely value them in his chosen steed. It is also lacks the speed and stamina of the White Horse from the side quest "The Royal White Stallion", which is a reference to the White Horse Zelda and Impa rode to escape from Ganondorf's Steed in Ocarina of Time, and may be a descendant of this White Horse.