DJ Sagara

"Get in your head already! You hate this world's rule of requiring sacrifices only for hope. Just smash them into bits. Smash it and change the world. Do you know why those Yggdrasill guys are acting the way they are? Because they're weak. They can only fight in the confines of that rule. They've given in to the cruelty of the world."

- DJ Sargara "We are those who've spread endlessly. We've surpassed the skies and prospered. We've stimulated revolution in ancient tribes...or perhaps I'm just the snake that they call me."

- Sargara revealed his true nature

DJ Sagara is the overarching antagonist in Kamen Rider Gaim. At first, Sagara seemed to be a "pirate" radio DJ of Yggdrasill Corporation, the position in charge of keeping the masses entertained, but in reality, he is the true manifestation of the Helheim Forest.

As Sagara, he is portrayed by Tomomitsu Yamaguchi.

Helheim Forest
The Helheim Forest (ヘルヘイムの森 Heruheimu no Mori), shortened to just "Helheim", is the main setting of Kamen Rider Gaim. It is the place which the Inves call home and where the Lockseeds are grown in abundance. Inves from the Helheim Forest are more powerful than the ones that are summoned by the Beat Riders. In order to enter this forest, one must have a Lock Vehicle, which can transport an Armored Rider at a sufficient speed, or find a random crack. The Yggdrasill Corporation somewhat also has a portal to the Helheim Forest in their base, which only someone who is from Yggdrasill knows about.

The Helheim Forest is a semi-alive place, having devoured entire worlds in its expansion, with its more recently discovered victim located in a valley. It is controlled by the Over Lord Inves, who control the plants and the very environment of Helheim itself. However, DJ Sagara is the very spirit of Helheim itself, making him the true ruler of the forest.

As Sargara
Believing that one must shine to be remembered by others, Sargara is a mysterious man whose only agenda is to see the future unfold in terms of who can obtain the power of Helheim Forest. Sagara originally supported the Yggdrasill Corporation, appearing to them via hologram, as the DJ of a pirate radio station to promote the Inves Games with his Beat Riders Hotline internet show. Sagara ultimately sets up much of Zawame's terms such as Beat Riders and Armored Riders. With the first group of Armored Riders no longer needed by the Yggdrasill Corporation, Sagara begins to show an interest in Kouta and secretly helps him escape while presenting him with the Genesis Core that Ryoma made for his Sengoku Driver.

In time, telling Ryoma Sengoku the location of the Golden Fruit while continuing to aid Kouta, the later after convincing Roshuo to give humanity a second chance, Sagara is revealed to be not human while originating from Helheim Forest and deeming Kouta worthy of using the Kiwami Lockseed. It was only after, the Golden Fruit is ultimately entrusted to Mai, that Sagara is revealed to be the will of Helheim Forest itself. As an immortal embodiment of the forest, Sagara's task is to observe and hasten evolution, explaining that only a Maiden of Fate can bestow the power of the Golden Fruit to one worthy of it. When Kouta is given the Golden Fruit and uses its power to transfer Helheim Forest's plants and Inves to a new barren planet with Earth remaining as it is, a surprised Sagara gladly accepts Kouta's wish. After seeing Kouta and Mai off while telling them to fill their new world with life, Sagara departs for another world (presumedly Inves' new homeworld) to repeat the cycle.

Trivia

 * DJ Sagara is symbolically tied to the image of a snake in several ways, including taking one's form to meet with the Over Lords, appearing before Ryoma Sengoku in a snakeskin suit, and being outright referred to as a snake by both Demushu and Redyue.
 * Sagara's overall snake theme comprises an Biblical allusion to the Book of Genesis, in which the Devil transformed into a snake tempts Eve into eating the Fruit of Knowledge, angering God and resulting in her and Adam being cast out of paradise.
 * Like the snake in the Bible, Sagara uses the Golden Fruit as bait to tempt many parties into actions with horrible consequences, such as Kouta's transformation into an Over Lord and Sid's death.
 * Additionally, some interpretations of the Genesis story say that the snake was either Satan himself or one of his servants, which can also be seen in Sagara's character as he makes several metaphorical "deals with the Devil", offering aid to those who need it but always with an implicitly sinister "catch" hiding in the shadows.
 * With Sargara being the representation of Helheim itself is similar to the Norse Mythology of Jörmungandr the World Serpent, which was said that when the Serpent releases his own tail, it will trigger Ragnarök.