Author's Note: Rook got some new aliens recently and sometimes that can be hard to keep track of. Since FFN doesn't like links, I'm going to make a list here of the forms that Rook now has access to and give a brief description.

Set I

Tidetail Wave

One of the creators confirmed that the Omnitrix has DNA of other Earth species, including the dolphin and white lab mouse. There is no canonical name for this transformation so I'm calling it Tidetail Wave. Dolphins' powers include swimming, echolocation, sharp vision, electroreception, mud rings/ mud nets, agility, intelligence, enhanced healing and ability to produce natural painkillers, holding their breath for a long time, and incredible speed in the water. Keep in mind that the Omnitrix creates the "ideal" version of a form so all these abilities can be used at a higher level than real dolphins. However, Rook loses the ability to communicate with others while in this form. In this AU, Tidetail Wave is Rook's equivalent of Ben's Wildmutt.

Archfiend

Archfiend is an alien we have seen in the series used by Benzarro but not Ben Prime. This alien has enhanced strength and durability and hellfire powers but I imagine that any kind of advanced fire techniques are something this alien must learn and just has regular fire powers by default. In this AU, Archfiend is Rook's equivalent of Heatblast or Swampfire.

Antigravitesla

Antigravitesla is one of Ben's aliens seen in the Latin American commercials. He has powerful gravity powers but lacks control over them. As a creative liberty, I gave him electrical abilities as well.

Terrorsaur

Terrorsaur is one of the aliens Tom Perkins, a designer who worked on Ben 10, created for fun after Omniverse ended. Terrorsaur is a winged creature with many eyes who has the power to create hallucinations. In this AU, Terrorsaur is Rook's equivalent of both Stinkfly and Ghostfreak.

Four Arms

You should know who Four Arms is.

Juryrigg

You should know who Juryrigg is. In this AU, Juryrigg Rook's equivalent of Grey Matter.

XLR8

You should know who XLR8 is.

Bloxx

You should know who Bloxx is. In this AU, Bloxx is Rook's equivalent of Diamondhead.

Kringl The Summoner

Kringl The Summoner is another one of Tom Perkins' designs. Kringl has the power to create ice and energy homunculi, in addition to having enhanced strength. In this AU, Kringl is Rook's equivalent of Ben's Ditto or Echo Echo.

Wildvine

You should know who Wildvine is.

Set II

Diamondhead

You should know who Diamondhead is. I decided to let Rook unlock Diamondhead because I wanted him to unlock a few aliens he's familiar with.

Upgrade

You should know who Upgrade is. I let Rook have Upgrade for the same reason as Diamondhead.

Rath

You should know who Rath is. I let Rook have Rath for the same reason as Diamondhead and Upgrade. In this AU, Rath is Rook's equivalent of Ben's Humungasaur, as he fills the strength slot of the second set.

Crashhopper

You should know who Crashopper is. I choose this one just for some balance.

Lodestar

You should know who Lodestar is. I choose Lodestar just because I like Lodestar, and because Rook doesn't have any aliens with similar abilities.

Shockrock

Shockrock is an alien from the reboot with the power to manipulate energy into solid objects or to use as an attack.

Slapback

Slapback is another alien from the reboot with the power to duplicate himself. Slapback is also very strong, durable, and heavy. In this AU, he is another equivalent of Ben's Ditto and Echo Echo.

Moot

Moot is supposedly the name Ben uses for his Highbreed form. Moot has super strength, enhanced intellect, projectile spikes, irrigation tentacles, and wings which gives him a very diverse powerset.

Funguy

Funguy is another Tom Perkins alien. His only known power is the ability to make incapacitating laughing gas. In this AU, Funguy is a weaker equivalent of Ben's Gutrot.

Warp

Warp is another Tom Perkins alien with the power to travel through time and space. In this AU, he is Rook's equivalent of Ben's Alien X. Rook will not have full access or mastery of Warp's powers for some time.