Kyo i indeed was rightWhy is above ? Don't they just do the same thing? Also, is it (like the transformation) or Greninja-Bond(the one with only stat boosts and no transformation)?
Skarmory and Corviknight may be the same typing but what they do are significantly more different. Skarmory is a much sturdier defensive wall than what Corviknight is, allowing it to do things that Corviknight is not capable of doing such as dealing with most of the strong physical attackers more reliably such as Baxcalibur, M-Tyranitar, M-Lopunny, Sneasler and others while also providing Spikes support.
Corviknight on the other hand lacks the physical bulk that Skarmory has but makes up for a more respectable Special Defense stat that lets it check things like Tapu Lele and use it as an opportunity to U-Turn, it may have been on a defogging duty ever since it was introduced but with the presence of Gholdengo, Corviknight has been relegated to being a U-Turn machine (just pivot in and out) in which options like Tornadus-Therian or Zapdos are usually better at since they're actually capable of doing something to what they're answering. It has also been experimenting with stuff like Sub Bulk Up due to Bloodmoon Ursaluna and also being a Gholdengo bait since most people would send it out expecting a defog but overall the mon is just really bad and has been memed on due to the high usage it's been getting despite being not that great.
The Ash Greninja reffers to Gen 9 Battle Bond which gives you +1 Atk, Spa and Spe and not the transformed one.