Ingward was one of the Sealers, sorcerers who flooded New Londo to lock away the Darkwraiths and their Kings after they descended into Dark. He's currently atop the ruins of New Londo, keeping watch over the seal that keeps the Abyss from spreading.
Ingward awaits the one that has obtained the Lordvessel, to grant him the Key to the Seal to drain water from the lower ruins in order to enter The Abyss. After the Four Kings are defeated, Ingward will move to Firelink Shrine.
Ingward is capable of removing Curses from the Undead.
Ingward wears a necklace with what appears to be a crescent moon which might tie him to the Darkmoon Covenant.