How good to know good Haiva's biology is not distrusted! He is slightly put at ease, but remains affronted and still seems on the verge of calling on Wei Wuxian and Wrathion to, by all means, test his legs.

Indeed, the legend has existed for decades. And it's proven true: during their war with the mermaids, the people of Alem have found that the sirens use small pieces of such glass to transform, gain human legs, walk the lands fleetingly and gather information. In truth, the shards seem to mostly grant their wish to transform their bodies, rather than explicitly 'give human legs.'