found myself rereading over the final stretch of Act 6 for whatever reason and on an archival readthrough the part where Typhon, head haloed in artifacts, has John simultaneously rid LOWAS of oil and rid the story of special stardust does read quite heavyhanded about the Typheus playing stand-in for Caliborn. which is an idea for which credit belongs entirely to an MSPA forum user long forgotten… but what never really hit me is this perhaps even more explicit association between Calliope and Echidna that comes pretty much right after

Jade, Jane and Calliope fall into the singularity of Calliope’s vortex and end up in a memory of Echidna’s lair, which has the above weird rift in it. beyond the rift is a white void where the Dead Cherub has been hiding, and she tells Calliope that she has served her purpose merely by arriving:
the reader seems to be led to believe initially that this rift is a unique construct of the Cherub’s in order to avoid being hunted down by English…

…only for it to be subsequently revealed that the rift is actually where Echidna herself lives (in contrast to the lairs of Typheus and Yaldabaoth, which are relatively tangible-looking locales). Echidna informs Kanaya and Karkat that
as the Dead Cherub leaves her hideout to create another black hole, Echidna releases the Genesis Frog; two sides of the same doorway, the black hole acting as a gateway back into Homestuck and the new universe acting as a gateway out. the two meetings literally bookend each other.