I shot into the sky just as the portal broke, and Armageddon flew after me and continued to release the fire while tracking me perfectly. I noticed that he was about to catch me because he was moving much faster, so I opened the spatial space behind me and the fire entered the portal.
I called on the Arcane Bird to distract Armageddon while I thought about a new strategy to use and the Arcane Bird flew in and released a sonic blast that made Armageddon wobble slightly. I didn't think that Armageddon would be this strong when I started fighting him. I at least thought that the Devil Spawn would be able to hold him down while the rest of us eviscerated him.. but I could tell now that this was not going to be an easy fight.