Ocularum

An ocularum (Plural: oculara) is a magical object introduced in Dragon Age: Inquisition. It is a skull (lacking the lower jawbone) which has a crystal in one eye. This crystal is visible through a hole drilled in the back of the skull.

They are found throughout the world, usually placed at high elevations upon short pillars. Their purpose seems to be to reveal the locations of magical shards (the subject of war table quest Investigate the Shards.) The player can look through the crystal, which will reveal the glow of the shards, after which they are marked on the map.

Vivienne later reveals that the oculara are made from the skulls of tranquil, if she is in the party while exploring Redcliffe. When a large number of tranquil skulls are found in the locked house near the docks, Cassandra says that she had noticed their disappearance, and that she should have looked harder.