I am experiencing the same issue, Offline Tools won't open. I tried reinstalling the latest version, but the result is the same. Everything worked fine until a couple of weeks ago. Offline Tolls version: 0.6.4 Mod version: 2.3.3 Windows 10
How do you manage to kill Xazax and Astrogha with this setup? The minions just hit Astrogha's totems so it heals every time. As for Xazax, I have tried with Rathma and VK. They damage Xazax over time but the screen gets too crowded with penitents and they eventually kill me.
Did you update the offline tool to a version that is compatible with 1.2.3? If not, you can check the offline tool topic to download the necessary file.