Board Thread:Questions and Answers/@comment-28154750-20160407232430/@comment-25600444-20160407233354

Final Phase is simply a given phase of a turn, like the Main Phase and Attack Phase. The "Final" means it's the last phase taken before heading into the next turn.

You don't have to defeat your opponent, or have the believed opportunity to, in order to enter Final Phase. You have the option to enter Final Phase whenever you desire. And there is no punishment for not defeating your opponent after declaring Final Phase.

How do you think the Lethal Formation Impacts and Secret Sword cards would work under those rules?

Like the Main Phase is for calling Monsters and Casting Spells, and the Attack Phase is for Attacking with your monsters and Items, Final Phase is simply another phase you can enter in order to perform certain actions, if you can.