We began playing High Heavens in 4-player mode and it has been really fun. For the most part, the rules remain the same. The main variants to the rules are:
1) Each player has 2 actions instead of 3.
2) Each player has 3 cards in hand instead of 5.
3) Play rotation is Team A player 1, Team B player 1, Team A player 2, Team B player 2
4) Cards that allow you to swap gods (Like Loki's Morph) allow players to take other player's gods.
5) We chose to play with open hands toward our teammate. You could however play with everyone hiding their hands.
We also played a pretty interesting variant, as mentioned on the Kickstarter page, where players stayed in "lanes". Player 1 on both teams stayed in the left 2 lanes plus the center lane, and Player 2 on both teams stayed in the right 2 lanes plus the center lane. This made the center lane a sort of danger zone as both teams could occupy those spaces. It was a really good variant but it admittedly messed with a couple of cards like Apparate (which lets the player place their next god anywhere on the map).