Rift of Beginnings

Just entered my first Rift of Beginnings having no idea what to expect since I couldn't find anything online on it.

Rift of Beginnings send you to a new rift with an Alter of Transcendence before a boss fight.

The boss itself has a few phases, I died at the 3rd phase when he got to around 30% life and started spamming the fireball explosion move. My build was cracked but I got a bit too lazy and thought I could just face tank it since I was healing 300+ hp every 2 seconds but it ended up 1 shotting me, so you will want to dodge them, you can simply dodge over all 4 rows of them.

That's all the info and advice I have so far. Will update once I can get back to the rift again. Please share if you have any other tips.