Similar for the most part to their close relatives (though they are purely carnivorous, with monstrous canine incisors and molars to match), deep sirens are prone to having bioluminescent features, extra limbs, fins, mouths, and/or eyes, as well as a less amiable temperament. However, despite this, deep sirens can indeed also use Epoch-Arcana to sprout legs. It would require additional help from Phasma-Arcana, however, to hide the glowing, flowing and/or sharp extremities they are known for. What they decide to do while treading land is a matter of legend, as it is mostly unheard of.