Balkiry, referred to as Valkyn (バルキーン) in the Japanese manual, is a red bird-like Badnik jet from the 16-bit version of Sonic the Hedgehog 2 found in Sky Chase Zone. They don't attack directly; they just charge quickly from the other side of the screen. Hit them anywhere to get rid of them.
The enemy reappeared in Sky Chase Zone from Sonic Pocket Adventure and Sky Fortress Zone from Sonic the Hedgehog 4 Episode II. They are also found in Desert Ruins Zone 2, Tropical Coast Zone ?, Sky Road Zone 3 and Hidden World Zone 2 from the Wii U/PC version of Sonic Lost World. In the 3DS version, they are only found in Sky Road Zones 1 and 3.
They have also made appearances in Sonic Runners and Sonic Runners Adventure, sharing their design from Sonic Lost World and generally found in Sky Road and Sky Sanctuary respectively.
Balkirys (Named Valkeens in the game's files, as a rendition of their romanized Japanese name Valkyn) reappear in Sonic Forces. In this game, they are found in Mortar Canyon and bomb Sonic in large numbers at high speed. Unlike previous appearances, they could only be avoided.
||A battle plane type bird robot last seen in "SKY CHASE ZONE" from "Sonic 2". A whole bunch of them can be shot out of Metal Sonic's weapon unit, "Metal Carrier", in Episode II.
— Sonic the Hedgehog 4: Episode II website