Dubior is a mid-boss appearing in Kirby's Return to Dream Land , Kirby's Dream Collection Special Edition, and Kirby: Planet Robobot. It yields the Spark ability when inhaled. It is first found in Stage 5 of Nutty Noon.
It is a UFO-like robot that has two yellow eyes and an antenna that has three strips of metal that change from yellow to red. Its head is colored in a shade of metallic yellow and the underside of it is a coppery orange. Surrounding Dubior are 5 stubs of floating metal that are detached from it. The tips are orange and the tops near its head are yellow.
Dubior's Extra Mode counterpart is pink in color and has only one eye. The underside of its head is now dark blue and the tips of the revolving metal around it are pink as well. Dubior EX has more health and its attacks deal more damage than the original's. Like other bosses and mid-bosses in Kirby: Planet Robobot, Dubior EX is renamed Dubior 2.0.
Dubior's attacks include a charged ram that deals lots of damage, a lightning-bolt attack from above that strikes repeatedly, and the ability to spawn Dubior Jrs. - miniature missile-shaped versions of itself (two in the main game and four in Extra Mode) which will zigzag around and may be inhaled to obtain the Spark ability. A great opportunity to strike is right after the charged ram, due to the fact that it will sit there stunned for several moments. When weakened, it will shoot several orbs of electricity from its bottom at wherever Kirby is. Even just moving around is a form of attack for Dubior, as it will zip about at random locations above Kirby's head. Dubior is usually fought before a puzzle that requires the Spark ability to complete it. Many of Dubior's attacks are similar to Kracko's and Kracko Jr.'s.
Dubior EX is a lot more unpredictable in battle. It darts around in the air much faster and charges more quickly. The charging attack is altered; sometimes instead of just charging ahead in a straight path, Dubior EX will loop in the middle of its ram to attack the player character if they try to jump. The Dubior Juniors it spawns are more numerous than before and make it harder for Kirby and his friends to avoid their flight patterns. Dubior EX can now use an altered version of its lightning-bolt attack. Instead of striking repeatedly, it sometimes fires along the ground and moves toward the player, much like Kracko's signature attack. It will do this twice in a row, pausing for a second before moving towards the player for a second strike.
- Dubior's normal coloration may be a homage to R.O.B..
- Dubior bears a bit of a resemblance to a mechanical version of a mid-boss from Kirby's Dream Land 2 named Master Green. Both are a shade of yellow (Master Green in his artwork) and give the same ability (Spark). The detached parts of metal that encircle Dubior's body somewhat look like short tentacles, further adding onto its appearance of a robotic jellyfish.
- Dubior is the only mid-boss in Kirby's Return to Dream Land (excluding Sphere Doomer) that is never fought with Planet Popstar's mid-boss theme playing in the background. The only Popstar stage it appears in is Stage 5 of Nutty Noon, where King Dedede's Theme plays.
- Gigant Edge is the opposite of Dubior in terms of the mid-boss music. It never plays Halcandra's mid-boss music but will always play King Dedede's theme in its second-to-last appearance. It does appear in Dangerous Dinner, but only during Kirby's Ultra Sword rampage in Stage 3.
- Dubior EX vaguely resembles Javelin Knight, one of the Meta-Knights.
- In Kirby: Planet Robobot, it's the only returning mid-boss that did not have a mechanized change to its design, as it was already a robot.