Once you've entered a battle there are numerous things you can do, such as blocking, dodging, or ki clashes as well as attack. To attack just take the stat you want to use (Ki or Stamina, we'll use Ki for this example) and take away power from your ki level, here's an example..
Cyril really hates whoever it is in front of him and charges a ki blast in his hand. Cyril fires it at unsuspecting someone. (Now you put your stats used, it is better to add all your stats- even the ones you didn't use because it makes it easier to keep up with things. It's still okay to only put the ones you used.)
Health:1,000
Ki: 1,000 - 100 = 900
Stamina: 1,000
Speed: 1,000
You choose how powerful the attack is by taking away from the stat, here I fired a ki blast worth 100 damage.
The opponent can dodge it by taking away 100 from their speed. This number will change depending on how much you put into it. If you put in 500 it will take 500 speed to dodge it. You can also block it using stamina. But there is another option if the attack is ki based. The opponent can also fire a ki blast that is stronger or equal to your blast and a ki clash is initiated. The two people keep putting more ki into it their blast until either someone runs out or someone lets the ki attack hit them. The accumulated ki from both parties hits the loser. Moves that combine ki and another stat can be used to clash into strictly ki-based attacks, but not the other way around. Two combination stat attacks cannot clash each other.
You can always flee if you're losing but you must have more speed than your opponent. The opponent may have a racial trait that wont allow you to run or an item with the same effect.
And that's how you fight! If you have any questions just ask.
