Holo Defense API is made up of four octahedrons surrounded by eight large and four small floating gray tablets, which spin around it. All four octahedrons have a bi-colored appearance; one is white and lime, one is red and purple, one is green and cyan, and the last is orange and yellow; these colors represent the boss each octahedron projects.
In The True Arena and Meta Knightmare Returns, an upgraded version called Holo Defense API 2.0 appears. This version has black tablets with blue etchings and cross-shaped crystals, along with a few color changes; the first crystal's white faces are now purple and yellow faces are now gray, and the last crystal's amber faces are now silver.
Holo Defense API mainly fights by summoning green, holographic versions of bosses from previous games in the Kirby series. Each boss is associated with one crystal—when it is destroyed, the corresponding crystal explodes, leaving only a wireframe of itself. All of the holographic bosses are weaker than their normal counterparts, although they compensate by attacking Kirby one after another.
Summoned by the white and yellow crystal. Holo-Kracko's attacks and appearance are similar to Kracko's boss battle in Kirby: Triple Deluxe. It shakes itself and drops a Waddle Doo into the arena, turns gray and unleashes a swirl of blue beams that spiral around itself for a short time, followed by swooping down to the opposite side. Other attacks include showering Kirby with rain, moving along the top of the screen while shooting electricity, and moving along the bottom of the screen.
Holo-Kracko is the third and final Holo-Boss to be refought in Access Ark Stage 5.
Summoned by the purple and red crystal. Holo-Doomers look like the Sphere Doomers in Kirby's Return to Dream Land, specifically the Regular Doomer and Fire Doomer. They are fought in a similar manner to the dual Doomer fight from The Arena of said game, and attack by shooting fireballs or swooping at Kirby. They can use a dive to sweep across the stage, and they can fire orbs which travel in a straight line. The red ones can be swallowed for the Fire ability.
The Holo-Doomers are the first Holo-Boss to be refought in Access Ark Stage 5.
When Holo-Ice Dragon falls, the Holo Defense API alters the background to reveal five large pillars. Next, the orange and amber crystal summons Holo-Coily Rattler, who acts similarly to his Kirby: Triple Deluxe counterpart. Unlike the other Holo-Bosses, he takes no damage unless an attack strikes his head, which appears blue. It fires three burning rocks from its mouth aimed at Kirby. These can be swallowed for the Spark ability. It can also do this move from the background. Then, it snakes its way across the stage, covering much of the ground with electric sparks. After that, it curls up into a ball and rolls across the stage. On the underside, it then turns around and rolls back onto the stage.
Unlike its fellow Holo-Bosses, Holo-Coily Rattler is not refought in Access Ark Stage 5.
Once the four Holo-Bosses are defeated, the Holo Defense API attacks directly. Emitting constant sparks, it flies haphazardly about the stage, jumping between foreground and background in an unpredictable fashion. Whenever it passes the battlefield, it leaves a star which can be used against it; a single blow from any of Kirby's attacks will finish it off, similarly to the fights against Adeleine. After several passes, the API will pause on the battlefield, releasing a star from either side; this is the best opportunity to land the final blow.
Once the API is defeated, it flies uncontrollably about the area, crashing into pillars, then explodes in a flashy manner. Kirby then does his victory dance and progresses onward to the next level.
Holo Defense API appears in its 2.0 form in Meta Knightmare Returns. The battles remain the same, but with increased attack power and speed. The "Holo" bosses appear in a purple tinge instead of green, and the bosses themselves have appearances based on their upgraded forms from previous games, with the exception of Ice Dragon, which had never previously had an upgraded form, so its appearance in this form is entirely new. Holo-Coily Rattler's head appears red. The crystals themselves are now stellated, rather than being simple octahedrons as before.
This hologram was created by analyzing data of the cloud monster who is believed to have inhabited the sky of this planet since ancient times. It excels at electrical attacks charged by the atmosphere.”
— Vs. Holo Defense API 2.0 • Kirby: Planet Robobot
They further analyzed the data of the cloud monster and discovered even more vicious attacks. The system redesign has implemented these attacks and made Holo-Kracko even more powerful.”
— Vs. Holo-Kracko 2.0 • Kirby: Planet Robobot
These monsters were created by Susie entering data she acquired from her travels. Where and when did she encounter the original monsters from another dimension? Who knows?”
— Vs. Holo-Doomers 2.0 • Kirby: Planet Robobot
This hologram was created from an ancient dragon. Dragons are no longer seen, but one of them may still be living quietly in a cave on an island somewhere. Who knows?”
— Vs. Holo-Ice Dragon 2.0 • Kirby: Planet Robobot
It is said that the People of the Sky who enshrined this monster still exist. It seems that the mechanization invasion has not reached them, due to their remote location.”
— Vs. Holo-Coily Rattler 2.0 • Kirby: Planet Robobot
This hologram was created by analysing data of the cloud monster believed to have inhabited the skies of this planet since ancient times. It excels at electrical attacks charged by the atmosphere.”
— vs Holo-Kracko (British English version) • Kirby: Planet Robobot
A hologram of monsters nested in an extra dimension. The original Doomers were red and blue. They love to eat Energy Spheres containing ancient technology.”
— vs Holo-Doomers (British English version) • Kirby: Planet Robobot
A hologram of a spectral dragon. This ancient life-form has lived through a number of ages. Most dragons breathe fire, but this blue dragon attacks with ice that it produces internally.”
— vs Holo-Ice Dragon (British English version) • Kirby: Planet Robobot
The hologram of the icon enshrined by the People of the Sky. Its weak spot is the data in its head. It was only a snake puppet full of powerful energy, but it used to be worshipped as a deity.”
— vs Holo-Coily Rattler (British English version) • Kirby: Planet Robobot
Redesigned by the Mother Computer, this defence system was also built based on the blueprint found on another planet. It's missing a portion of data and unable to demonstrate its full potential.”
— vs Holo Defence API 2.0 (British English version) • Kirby: Planet Robobot
Further analysis of data from the cloud monster has uncovered even more vicious attacks. The system redesign has implemented these attacks and made the Holo-Kracko even more powerful.”
— vs Holo-Kracko 2.0 (British English version) • Kirby: Planet Robobot
These monsters were created by Susie entering data she acquired from her travels. Where and when did she encounter the original monsters from the extra dimension? Who knows?”
— vs Holo-Doomers 2.0 (British English version) • Kirby: Planet Robobot
This hologram was created from an ancient dragon. Most believe dragons no longer exist, but one of them may still be living quietly in a cave on an island somewhere. Who knows?”
— vs Holo-Ice Dragon 2.0 (British English version) • Kirby: Planet Robobot
Holo Defense API closely resembles Pix, the boss of Rock Star in Kirby 64: The Crystal Shards. Both are technological bosses resembling multiple floating crystals, which shatter and leave only their wire frames after being defeated. In addition, they are also the second bosses to be fought in both games overall.
This is because, after Susie's disappearance, President Haltmann gained access to numerous worlds to travel to, allowing him to collect the data (presumably from Rock Star).