I usually play Sedna as a tank / healer.
Buy Monks at the start, Blood of the Fallen as your Favor item, Heal as your starting skill.
After that, I tend to play on the defensive side, trying to stay alive and keep my teammates alive, going for Healing Wind when available, at least lvl 2 of Inner Grace before getting Pounce.
Items are simple. Scaled Helm, Banded Armor, Hauberk of Life, Vlemish Faceguard. Upgrade as needed, though I doubt you'll need to upgrade the Helmets, I usually don't. Also, upgrade your Monks whenever you can (at least until High Priest, Bishop is tougher but heals less), and get the Siege Idol too (lower priority).
Spice up with items you like, for better offense, mobility or survival.
