Flaeneath is a deserted island, but not only is it deserted, it is desolate. Thousands of years ago the island was separated in two by a mountain (this still holds true today, though); on one half was a lush, green forest and a rocky plains; on the east, another forest, but one that was dwindling during the last days of the inhabitants.
In modern times there are no more phial. As for Flaeneath, the weaponry—incredibly advanced for its time—caused so much destruction that life was wiped out on the island. Forests were decimated, and then the remaining 90% was also destroyed. The very soil on the island was degraded and left unsuitable for growth. All that remained on the island was junk and scrap left over by the phial, and the island became a wasteland.
Needless to say, the slubes left the island, and they settled on the island Hackney.