Word for combination of strength and agility

Solution 1:

For an RPG player attribute, I think "conditioning", "vigor", and "might" all work pretty well.

Solution 2:

Prowess might be a good single word choice. You can be more descriptive by using physical prowess.

Merriam-Webster offers this definition: "extraordinary ability" and "He is know for his prowess on the football field." shown as an example in a sentence.

Solution 3:

Physicality might fit the bill here.

The physical attributes of a person, especially when overdeveloped or overemphasized.

Otherwise, I'd elect to use the global term fitness. Someone who is fit is a good combination of strong and dextrous.