Combo attacks are when an axie attacks with two or more cards in a round. Combos will add a little bit of damage based on the skill of the axie playing the combo. The higher the skill, the more bonus damage.
The formula for calculating combo damage is: (attack * skill) / 500
An aqua with 35 skill plays two cards: Hare (120 damage) and Hungry Bird (110).
Combo Attack Notes:
* The formula isn’t exact. In my testing it can be off by 1 or so (maybe due to decimals and rounding) but it gets you in the general ballpark
* Playing more cards in a combo does NOT increase the combo bonus. The formula is the same for each card played whether is a 2 card combo or 4 card combo.