So, the Avengers 3 Infinity Wars movie had a new shield for Captain America that would make for an awesome Buckler design inspiration.

The SSG crew could design something similar and make it out of Crystal and give it some effects that would make it unique and desirable regardless.

1 effect could do this!

Making a legendary version of said item would then also mean making a legendary version of soul eating in which would be like legendary affirmation but with the addition of inflicting negative levels on your enemy as well as temporary hitpoints!

And what's more is that thematically speaking you could also add cursespewing to this buckler.

Mind you I believe soul eating should not only be brought back, but improved on to be more in line with the level scaling of legendary affirmation, like offering 100 temporary hitpoints in the heroic version and 1000 in the legendary version, while the negative levels should just be treated as flavor, so maybe 1d6 heroic and 1d10 legendary at most.

The point of temporary hitpoints is to occasionally negate some incoming damage (Enough to represent a sigificant attack from an enemy)