One of the prizes for my Dragon Pillars giveaway earlier this year was an original set of five character sketches, including the four Pillars and Senka. The original sketches are being sent out as a prize, but I scanned in the arts before sending them off. They are all done in ink.
The portraits are of: Garred, the Water Pillar; Senka, the Archivist; Shula, the Fire Pillar; Juris, the Earth Pillar; and Cua, the Wind Pillar.
You can see a high res version of each individually on my Patreon.