Lana opening a dimentional gate on Rebound p. 127.

Seraphim are the gatekeepers of Heaven. These angels' sole job is to make (or close) cross-dimensional gates, often between Heaven and Hell, since Hell is not otherwise easily accessible to angels. Their ability to make these gates is granted by their halo and requires a combination of specialized magic and drawn spells/sigils in the ancient Malachim language.

The title of seraph is very highly regarded and is usually given to long serving generals as a form of semi-retirement.

Seraphim have four, white wings, one set smaller than the other, as well as a golden disc for a halo.