Dark skin even for a Twili, with brilliant purple eyes bloodshot (not in red but purple)
The clothes on his back, and his Dusk-corrupted blood.
Strengths & Abilities
Crazy-mad orator (think The Prophet Masema from The Wheel of Time). His Dusk-corrupted blood gives him the power of Duskblood magic, a dusk-corrupted form of blood magic (duh).
Duskblood Magic requires sacrifice, so he's rather powerless without minions (unless he hurts himself to cast his rotes)
Before his 'awakening', Penumbra was simply Jacob Hwelitt. Jacob was born a common citizen, and joined the Army at the age of 16. He trained as a normal soldier until his aptitude with Twili Shadow-magic was discovered in a normal screening. He was then enrolled in the Magos Training and came out top of the class. That was when he turned 21. With his honors he was promoted to first lieutenant, and when the Army marched off to Hyrule he was included among the men of the Expeditionary Force.
During the Battle of Ordon he was injured, and was not within the range of the Forest Medallion's explosion. His injury also resulted in him being left behind in the village while the rest of the Advance Army marched further into Hylian territory and proceeded to assault Castle Town. However, with the arrival of Regent Ambershade came also an increase in organization of the Ordona Province, and a new head medic to deal with the invalid. First Lieutenant Hewlitt was among the soldiers given priority healing, and is now being cleared for release from the temporary military hospital, his Shadow Magic being required by the Regent to assist in setting up infrastructure via Shade-Portals.
During the repair process, there was an obscene accident, and Jacob was exposed to the raw powers of the Warp, the Dusk Realm. In his time in this maddening realm, Jacob's body was transformed, his blood corrupted, and his mind invaded and twisted. When he was spat out again in Castle Town, he emerged as Penumbra. He called himself "Penumbra, the Harbinger of Umbra" and appeared to be aligned with neither Twili nor Hyrule. He broke into Hyrule Castle Cathedral with no heed for the religious sanctity of the place, and murdered the High Prelate in order to cast his first Duskblood magic, creating a Duskblood Golem that ravaged the Sactuary and exploded in a bilious cloud of blood-corrupting Dusk. The congregation gathered was infected, and turned to the worship of Penumbra and the Dusk.
For the past six months, Penumbra has been growing his flock of black sheep, corrupting the survivors in Castle Town, Hylian and Twili alike, into his Duskblooded Horde. No one knows what he plans when the congregation grows large enough, but those who are aware of his increasing fellowship know that it can't be good. The Horde, however, works as tirelessly as he to grow their numbers, fervently hoping the next convert will be the last needed for Penumbra meet his aim and 'Bring about the coming of Umbra'.