Carl could just kill the AWA on his next turn if we don't keep it up right now

Not defending would get him down to 1HP now, then even defending Carl would kill him

This way we can use up Shuri's feat to keep the AWA alive longer, and the spell won't be wasted, so it gives us somebody to sacrifice. Shuri does the same damage to Abydos as Ar4chez4n anyways