Sebastian takes on the appearance of a tall, handsome adult, standing at an impressive height of 6'1". His striking features are enhanced by his jet-black hair, which falls in sleek waves, framing his sharp jawline and high cheekbones. His reddish-brown eyes are particularly captivating, glowing with an almost otherworldly light; they blaze a bright red when he is agitated or angry, and shift to a bright fuchsia hue when he is aroused or feeling playful.