Who's This? A radioactive skeleton.
How you could have heard of him: He cuts a distinctive figure, so while he's rarely used as the focus of a story, he does appear in the background a lot in the contemporary era. He will apparently be a member of HBO's Creature Commandos (voiced by Alan Tudyk).
Example story: Detective Comics #825 (January 2007) "The Return of Dr. Phosphorus!" by Royal McGraw, Marcos Marz, Luciano del Negro and John Kalisz
One of Phosphorus' originators is dead (his pal just horribly burned). He next goes after another scientist who was involved, but Batman is waiting for him.
So does Dr. Phosphorus deserve a place in Batman's Rogues' Gallery? Sure. The horror elements work well, etc. But perhaps Firebug is a more versatile fire-related villain for the Bat. All in all, it probably made sense that Sartorius had his best years in Starman's Opal City.
Who's Next? A magnetic madman.