There is finally an image available for this promo card. This card was being given away as a store promo for the Q3 Marketing kit for Darkness Ablaze. Now store are recieving them. It has a stamp with 'Thank You' on the promo. Looks at least the US and Canada stores have access to these Marketing kits, you need to order them in order to get this plus other materials.
Last time we thought this was going to be the store promo for Darkness Ablaze in Europe too, but that is Corviknight.
Thank you to our friend PlaySkapeGames for sharing the image!
Old story from 22-7-2020:
Hydreigon from Sword & Shield Darkness Ablaze will be the next store promo if you spend a certain amount of money on Pokémon products in participating stores.
It will likely (not confirmed yet, since there is no image to confirm this now) have an exclusive cosmofoil version with the Darkness Ablaze set logo. Also it's currently unknown if the regular version is a Holo card or Regular Rare in the Darkness Ablaze set list.
This is not a Darkness Ablaze Prerelease promo card.
More images and details on how to obtain this card in other countries will follow soon when Sword & Shield within the upcoming weeks. So you are advised to keep your eyes open and check/ask your national toy/game stores during release.