Pick up to five heroes and, if you like, the enemy squad: the faction team bonus and who takes less damage from whom.
Your squad
no heroes. No team bonus.
Bonus tiers: 3 heroes of one faction +5%, 3 + 2 of another +10%, 4 +15%, 5 +20%.
Enemy squad
Only faction rules are counted: hero levels, stars, gear and skills decide the fight as well.