Is it possible?

[Anna]

I think you are. Blackmoor is a part of the Flanaess even, north of Iuz homeland is a barony named Blackmoor. I have a PDF of the original Blackmoor but I haven’t read it yet so I can’t say how well they are in tune.

The Petal Throne and Mysteria I don’t know anything about so I suggest you ask about them all at Canonfire.

//Anna

[NeonKnight]

Mystara (not Mysteria) was a separate Campaign world from Greyhawk, but like Greyhawk had it's own version of Blackmoor present within in:

http://en.wikipedia.org/wiki/Mystara

Blackmoor

Mystara (like Greyhawk setting) also incorporated the Blackmoor setting by describing Blackmoor as evolving from a feudal kingdom into a highly advanced civilization, which existed in the distant past. The culture of Blackmoor unfortunately utilized more and more powerful, and destructive, technology. It ended itself in an apocalyptic explosion so devastating that it changed the climate and geography of the planet as a whole.

As to the Empire of the Petal Throne, from Wikipedia:
http://en.wikipedia.org/wiki/Petal_throne

Published works

Barker was a Professor of Urdu and South Asian Studies at the University of Minnesota during the period when David Arneson, Gary Gygax and a handful of others were developing the first role-playing games in Minneapolis and Lake Geneva, Wisconsin. Barker tapped into this tradition to explore and develop the Tékumel setting. His "Thursday Night Groups" were some of the first roleplaying sessions anywhere and provided what was, at the time, a unique, week-by-week development of the setting.

In 1975, Tactical Studies Rules, Inc., the publishers of Dungeons & Dragons, published the Tékumel fantasy setting as a standalone game under the title of The Empire of the Petal Throne (a synonym for the Tsolyáni Empire). It brought a level of detail and quality to the campaign setting which had previously been unknown in the RPG industry, and could be considered a turning point away from the tactical roots of RPGs. The game was the subject of articles in early issues of Dragon Magazine, but factors including inconsistent support from TSR led to its decline in popularity. Over the subsequent thirty years several new games based on the Tékumel setting were published, but to date none have met with commercial success. While published as fantasy, this edition of the game is sometimes classified as science fantasy and erroneously as science fiction.

Finally, as to Frank Mentzer's Aquaria, the wikipedia entry lists the following nugget:

http://en.wikipedia.org/wiki/Frank_Mentzer

# The entire RPGA series of adventures based on Mentzer's own home "Aquaria" D&D campaign, coded R1 through R10. The R series of adventures was originally intended to form the basis of a new "Aqua-Oerdian" boxed set to expand upon the World of Greyhawk campaign setting, but these plans were shelved after Gygax left TSR in 1985.
# Module I-11, Needle (TSR, 1987).