It’s already in the game. You just need to assign its animation to an item you want.
Just import its sounds first from FE6 since it kills BGM.
It’s actually not in fe8, it’s in fe7. So you would need to import it
I looked on Serenes Forest and the graphic repository (Emblem Anims) but it doesn’t seem to be there…
exaccus range animation does not exist in FE8U.
It exists in FE8J but has been deleted in FE8U.