The patch notes for the Diablo themed Eternal Conflict update are enormous. There's a huge amount of changes for heroes, maps and everything in between. You're going to need a coffee when you read through it. As for the highlights:

1. There's a new Hero called The Butcher. Anyone who has ever played Diablo will be familiar. 

2. There's a new Battleground called the Eternal Conflict (surprise!)

3. Lost Vikings have been nerfed, somewhat heavily.

4. Some Stun skills have been converted to Daze as these were too powerful at locking down. 

5. Some Unstoppable skills have also been adjusted across various Heroes. 

6. Murky receives a slight buff. 

7. Possession for Sylvanus has been buffed and changed significantly. 

8. Brightwing has received a major overhaul of her talents and some skills. 

9. Rehgar and Malfurion have also received significant changes to their talents and/or skills. 

10. There's tons of bug fixes. 

We'll be putting the update through its paces when it goes live later today (around 6pm PDT) and will be sure to update our Heroes of the Storm build guides.