The effect on the legend Grombrindal says:

"Each unit you control gains #(1power) if a zone is burning

http://deckbox.org/whi/Grombrindal

Does that mean only the dwarf players zones or any players?

Any players.

Great card in Cataclysm

But hasnt tested it but tomorrow I hope I will find out.

Thanks for the help as ussual

It is any unit controlled by Grombrindal's controller.