They managed to get hold of a heirarch modron (a decaton) but found someone was already there: Baator-tan. (I pulled the OP image from 4chan and used it as a character design for her.) She was there to negotiate a contract with the March to gain baatezu protection through the Lower Planes in exchange for Blood War troops, but was willing to step aside and let the PCs deal.
It didn't go well. The modrons denied all requests to move and suggested that it was their fault for changing the roads, and the modrons were willing to trample anyone who got in their way (an oddly harsh response for a modron). On top of that, Bleaker-tan was currently in a depressive slump after her attempts to cure Pandemonium-tan of insanity were foiled by the latter's escape from the Gatehouse, and was no help.
Baator-tan filled in gaps in their knowledge about the March and what they could do while mocking the PCs and Celestia-tan; she revealed the latter one was wrapped up because she was actually an ugly-as-sin tiefling playing at being an archon.
This turned out in the PCs favour when Bleaker-tan finally had enough of Celestia-tan being bullied and snapped out of it in time to show Baator-tan what she had recently spent character points on: wrestling moves. Baator-tan was trapped in a headlock and swung around before being hurled away into the horizon Team Rocket-style.
That is pretty much all that happened. The PCs tried a few things while Sensate-tan (the fastest flier) flew off to warn Heart's Faith, including Revolutionary-tan disguising as a modron to try and stir up the ranks. It's slowing them down for a bit, but they know it's only a matter of time before the unswerving modrons reach Heart's Faith, and they're running out of time.
Next week: Hopefully no orphans will get stepped on.