Complex sentence: Joss Whedon "Astonishing X-Men" apparently contradicts it by showing Cassandra Nova still in Stuff's form, but this does not rule out yet the possibility that Ernst may very well be in fact a derived part of Cassandra Nova.
Split into simpler sentences: Joss Whedon "Astonishing X-Men" apparently contradicts it by showing Cassandra Nova still in Stuff's form. These attempts at retcons however have not successfully ruled out yet the possibility that Ernst may very well be in fact a derived part of Cassandra Nova.