You should contact the auctioneer(s). May be a local or fan artist.
Looks like it was done by Blm.
It's a nice Joker/Harley piece. But it doesn't look like any regular comic book artist.
There came a time when the Old Gods died! The Brave died with the Cunning! The Noble perished locked in battle with unleashed Evil! It was the last day for them! An ancient era was passing in fiery holocaust!