The Baneward is an artifact in Tyranny.
The Forge-Bound succeeded in infusing this shield with the essence of fallen Bane.
Using the Bane for creative purposes is not a new practice, but has roots in more failure than success. Since the creatures leave precious little by way of mortal remains, not as much can be gained by harvesting them as the truly curious would desire. The trick is not necessarily gathering the ethereal resource in large quantities, but knowing what to do with however much Bane essence is available. In this case, the Forge-Bound took a lesson from past craftings and relied on runes attributed to an ancient Archon of Thralldom. In his time, the Archon was known for his interest in the Bane and any means of taming them as useful servants.
This confusing and much-neglected branch of the arcane opened up the means to bend the essence to the smithy's will - if only long enough to form a rudimentary shape. The Baneward shield bends at an angle that implies a struggle to find a coherent form.
Something of the ethereal creatures must live on in the shield, as it occasionally twitches with pent-up aggression.