Professor Kurata Akihiro was also part of the Suguru exploration team. When a Lynxmon jumped he fired a shot at it. Since then he thinks all Digimon as evil. He is the one who set about with a team of military destroying Digimon including Yukidarumon (Ikuto's Digital Mother). He created his own Digimon Gizumon and even turned 3 humans into Bio Digimon in order to bring his plans into being after He found Belphemon's Digitama and revived him with all the Data that his Gizumon gained along with the Bio 3.

Not only did he revive Belphemon he had a bomb put around Relena's neck in which Touma agreed to help him to control Belphemon. When Touma tricked Kurata he turned himself into energy and fused with Belphemon. However Belphemon started to control him. When ShineGreymon + Masaru defeat Belphemon, Kurata opens a huge portal to the Digital World this is the final phase that makes Yggdrasil want to get rid of the Human World. But it appears in opening that portal he pays the ultimate price.

Attacks: Lampranthus + Eternal Nightmare
Level: Ultimate
Kurata brought Belphemon back from a Digitama and created him in his Sleep Mode by using Data from other Digimon so he could rule the worlds. He was able to control Sleep Mode with a device Touma made as part of their deal due to him knowing of Relena. When Touma blew up the device he couldn't make Sleep Mode move so turned himself into energy so Sleep Mode, Mode changed.

Attacks: Lampranthus + Eternal Nightmare
Level: Ultimate
When Kurata shot himself into Belphemon Sleep Mode he changed into Rage Mode and started blasting at the Savers. Soon enough Belphemon took over from Kurata to do his own thing which was blowing up everything he could. It took Agumon evolving into ShineGreymon Burst Mode and a well aimed punch from Masaru into the 'face' of Kurata to take him down.

Royal Knights
For more info on the RK's you can see their page, the ones to be seen in Savers are as follows:
Alforce V-Dramon
Dukemon
Dynasmon
Lord/Rhodo Knightmon
Magnamon
Omegamon
Cranniumon
Sleipmon
Duftmon

Attacks:
Daimon Suguru went to the Digital World 10 years ago, we know he met Mercurimon and went in search of Yggdrasil. It appears he has turned into Yggdrasil and has ordered that the Human World be destroyed....it now also appears that he doesn't care for Sayuri, Chika or Masaru.

Attacks:
When the truth about Suguru is revealed the true form of Yggdrasil is shown. He is still hellbent on destroying the Human World. When beaten by Masaru we see another 2 forms of him.