This weird, Murloc-esque stuffed animal was revealed on September 17, 2011, to be sold exclusively at Blizzcon 2011, to show attendees and virtual ticket subscribers.
The plushie costs $16. No dimensions have been given, but presumably it's about the size of a breadbox.
The official production description:
"Peanut butter and chocolate has got nothing on hellfire and amphibious creatures! Burning with badass-ness, the Diablrgrl Designer Toy is a limited edition import and comes complete with a soulstone-jammed skull ready for display. "