Combat

When it's time to swing, you enter combat. The combat layer is broken into Rounds, units of time 2d6 seconds long. Characters take actions in a Round in phases; Positioning, Offensive, and Utility, as well as reactions, reactive actions, and free actions. Actions are declared at the beginning of their respective phase, and then resolved simultaneously. When no creature wishes to take any more actions in a phase, that phase ends and the Round moves onto the next one, or to the next Round.

In the Positioning Phase, actions such as Move and Reposition allow you to get around the battlefield. In the Offensive Phase, actions such as Cautious Strike and Grapple allow you to inflict pain and get one over on your foes. Finally, in the Utility phase, actions such as Use Item and First Aid allow you to interact with your equipment and take a step back to gain an advantage. Reactions and reactive actions can be taken at any time in response to their designated triggers. Only one reaction or reactive action can be used in response to any given event. In addition, you take a cumulative -1 penalty for each reaction or reactive action you take after the first in a Round. There are four reactions every character has access to; Dodge, Focus, Interpose, and Tank.
Reactive actions are a special kind of action. You declare them as normal during the appropriate phase, along with a trigger. They do not resolve until this trigger is met or the action is abandoned. They can be abandoned in the same Round they are set to regain the spent action, but still count against the multiple reaction penalty. They are usually automatically abandoned if the character takes any other action with matching mental, move, or physical descriptors, at the GM's discretion.
Free actions can be taken at any time according to their particular criteria.

Typically, a creature can take two actions per Round, plus an additional action at a cost of 1 STA. Additional actions after the third, if an effect grants them, also cost 1 STA each, and reduced actions take from the 'free' actions first.
For instance, a character benefiting from magic that grants them up to four actions every Round would have to spend 2 STA to take this fourth action; 1 STA for the third action and 1 STA for the fourth action. On the other hand, a character who is Staggered would have to spend 1 STA just to take two actions!

In combat and dialogues, Momentum is a special resource used to abstract moment-to-moment advantage and initiative. It will raise and lower frequently as enemies trade blows. If a character in a combat ever has 0 or less Momentum, they are Staggered until they reach 1 Momentum or more.
A character starts with 1 Momentum unless they were surprised by combat starting, in which case they start with 0.

For a list of combat actions, see here.