Demushu

Demushu is a red Over Lord Inves and one of the few survivors of the Femushinmu civilization. He serves a major antagonist in the "Helheim Invasion" saga of Kamen Rider Gaim.

Kamen Rider Gaim
After being transformed into an Overlord Inves, Demushu massacred the weaker of his own kind.

When Kaito was searching for Demushu, the Over Lord Inves summons several Elementary Inves to attack Baron so he can escape. Yggdrasill's Secret

Kaito tries to lure out Demushu by leaving a pioneer plaque and a Japanese Dictionary for it to pick. Demushu later finds Kaito in the ruins and destroys the plaque and the dictionary. Kaito then transforms into Baron and tries to fight Demushu, but the Overlord Inves easily overpowers the Rider and pins him the ground. However, he is saved by Kamen Rider Marika, who distracts Demushu, giving them time to escape.

Demushu later attacks Gaim as he is searching the ruins. However, right before Demushu could defeat Kouta, Redyue stops him so she can bind Kouta with the Helheim plants.

Demushu later fights Kaito again, this time on much more equal footing. However, their battle is interrupted by both Gaim and Redyue, with the latter telling Demushu to retreat.

Demushu soon begins searching for Kaito again, attacking several researchers along the way. He eventually comes into conflict with Zangetsu Shin and Gaim, however, Rosyuo orders him to retreat and telepathically tortures the red Overlord until he does. Rosyuo later punishes Demushu when he returns for attacking the humans.

Demushu later has a rematch with Gaim and Zangetsu but Sigurd soon appears and challenges him instead. Demushu soon notices that a crack had opened and enters through it.

The crack takes him to Zawame City, which he begins to destroy upon his arrival. Gaim and Baron try to defeat him but fail, with Demushu beating both of them back. Demushu tells Kouta that he lives for battle and that the weak won't survive, causing him to become enraged and transform into Gaim Kachidoki Arms. and battles with Demushu. Demushu looks to be on the brink of defeat, but Marika and several Kurokage Troopers interfere with the battle, hoping to capture Demushu. This allows Demushu to gain the upper hand, but Kouta escapes alongside Kaito. Baron, equipped with the Lemon Energy Arms, fights Demushu alongside Marika, Armored Rider Knuckle, and the Kurokage Troopers.

Demushu retreats to a place with Helheim fruits and eats one, allowing him to assume an Evolved Form. Demushu easily defeats the Riders on Earth, with Duke leaving them. However, Kouta arrives and uses his Ultimate Form equipped with the Kiwami Arms to destroy Demushu.

Super Hero Taisen GP: Kamen Rider 3
Demushu was among the many villains in service to Shocker after their History Changing Machine rewrote the timeline. Though manages to kill Kamen Rider Mach he is by Gaim using his Orange Arms' Burai Kick.