Senses

Blindsight

Source: Player’s Handbook p. 183. Available in the SRD and the Basic Rules.

A creature with blindsight can perceive its surroundings without relying on sight, within a specific radius. Creatures without eyes, such as oozes, and creatures with echolocation or heightened senses, such as bats and true dragons, have this sense.

Darkvision

Source: Player’s Handbook p. 183. Available in the SRD and the Basic Rules.

Many creatures in fantasy gaming worlds, especially those that dwell underground, have darkvision. Within a specified range, a creature with darkvision can see in dim light as if it were bright light and in darkness as if it were dim light, so areas of darkness are only lightly obscured as far as that creature is concerned. However, the creature can’t discern color in that darkness, only shades of gray.

Truesight

Source: Player’s Handbook p. 183. Available in the SRD and the Basic Rules.

A creature with truesight can, out to a specific range, see in normal and magical darkness, see invisible creatures and objects, automatically detect visual illusions and succeed on saving throws against them, and perceives the original form of a shapechanger or a creature that is transformed by magic. Furthermore, the creature can see into the Ethereal Plane.