Whether you're trying to effect a comeback after losing two idols or trying to keep your momentum when you're in the lead, it's important to know in what order things will happen when you hit the End Turn button. This guide aims to succinctly clarify what happens during that time.
Only units whose Countdown is 0 at the time of your hitting the button will attack (with the exception of Irva, who makes a ranged attack immediately after a friendly Undead deals damage regardless of her Countdown). Units such as Harvester and Gravelock Freak will not attack even if their Countdown is set to 0 midway through the turn.
Before combat begins, scrolls which carry "before attacking" attributes such as Blightbearer and Ember Bonds activate.
Units attack in the order shown in the picture above, with the front column attacking first, the middle second, and the rear last. Units higher up attack first until the end of the column, at which point the next column attacks.
When a unit deals damage to a unit, any "when attacked" attributes on the unit activate, such as for Vitriol Aura, Puppet Soldier and Spiky units. Additionally, any "when dealing damage" attributes also activate on the unit dealing the damage. If the attacking unit is Relentless, it will continue its attack until its attack value has been exhausted, at which point it will return to its starting tile. Only then will destroyed units be resummoned, such as units enchanted with Seed of Insurgency or Humans adjacent to a Witch Doctor.
Pillage traits will activate at the same time as the unit deals damage to the idol (although Wetland Ranger will not grant an attack bonus until the beginning of your opponent's next turn). When a player's first idol is taken down, Dominion traits will activate for the other player for the remainder of the game, including the remainder of the attacking player's turn. So when moving your units, make sure your Wings Cleavers and Blade Husks will attack after the idol is destroyed.
The end of your turn is marked by the triggering of scrolls such as Searing Shackles.
The beginning of your opponent's turn is marked by the activation of "when Countdown becomes 0" attributes such as with Honorable General. Simultaneously, Poison damage is dealt, along with "at beginning of turn" damage such as from Overdrive. The order in which Poison damage is applied is not entirely clear, meaning whether or not the Witch Doctor will summon a Husk adjacent to itself before it, too, is destroyed by poison damage is anyone's guess.
That's it! Now go show off your newfound mastery of what happens after you click the hourglass in battle!
Sysp explains some of the nuances behind card sacrificing.