How does Mario’s M-Power technique work?

How much extra damage does M-Power grant?

At first, it increases attack damage by 20%. This means that attacks that do more damage will benefit from the increase more than other attacks! It also means that crits are more powerful.

This can be upgraded using skill points to 30%, 40%, 50%, and finally 70%.

How much range does it have?

At first, it affects all allies within 4 spaces. This can be upgraded up to 7 spaces.

When you select the ability during combat but before you use it, you can see a green border showing you the ability's range, and any allies who will be affected by it will glow blue. In addition, you can use the Tacticam at any time to see the ability's range, even when it's on cooldown or before starting battle.

Does the ally need to be in range when the ability is first activated, or is it based on where you attack from?

The allies need to be in range when the ability is first activated. After that, they can be moved out of the ability's range in order to attack without losing the damage bonus. It's treated as a buff that ends at the start of your next turn, so be sure to place the buff on a teammate before they attack for the turn.