Recently, magazine scans for Kamen Rider OOO's upcoming full combo is leaked. Kamen Rider OOO Shauta Combo is rumored to show up this February, since OOO Tajyadol Combo will show up before it in the series and it is confirmed on Episode 20.
Kamen Rider OOO ShaUTa combo utilizes the Shachi (Orca), Unagi (Eel) and Tako (Octopus) Core Medals from the blue and water based Greeed, Mezool who died in Episode 16: An End, the Greeed, and a New Rider. And since these Core Medals are in the hands of Kazari, it's highly possible Eiji and Ankh got these from him.
OOO Shauta Combo's Unagi Core Medal has an ability to utilize Unagi Whips which has an ability to electrocute any enemy. This confirms that it's not just a normal eel, but an electric eel! The Unagi Whips were first used in Episode 18: Destruction, Motives, and the Eel Whip.
The name for Kamen Rider OOO Shauta Combo's Scanning Charge is called Octo Vanish. As you can see in the scan above, it will be a whirlpool, tornado or drill-like rider kick! And similar to the rumors before, during Scanning Charge, OOO ShaUTa's legs will have four to eight legs to represent the tentacles of an octopus.
Minor update with info coming from DecaEnd.