At the start of each of your turns, roll a die to see if you get an extra standard action. If your roll is equal to or lower than the escalation die, you get an extra standard action that turn.
At the start of battle, you roll a d6. Each time you successfully gain an extra action, the size of the die you roll increases by one step on the following progression: (d4), d6, d8, d10, d12, d20. If you get an extra action after rolling a d20, you can’t get any more extra actions that battle.
Once per day, start a battle rolling a d4 for elven grace instead of a d6.