Build Guide
This is the standard Firebird archon build with a few tweaks to kill Diablo in 45 seconds for the seasonal journey guardian. Some people have complained that getting the seasonal journey is difficult with the Firebird build. It is very easy with this build. It maximizes boss/ elite damage and allows you to do incredible damage. You could even swap teleport for Familiar- Sparkflint if you needed to, but being able to teleport on the boss is probably more important. This build is for nothing more than defeating a boss very quickly. Do not attempt to play this build in any way other than for the achievement.
I played with a friend and I transformed and 1-shot phase 1. Then I 1 shot phase 2. halfway through phase 3 I left archon form, and my friend and I finished the fight. He said afterward that he loaded into a load screen to go to phase 3. He never even saw phase 2. Good luck have fun.
Thank you, it worked for me! Finished in about 43 seconds on 2nd attempt with this build. I did stack the 20 arcane torrents prior to entering and I also adjusted all graphic settings to minimum to maximize video and loading performance.