Omniguard was an alien race with some sort of shared consciousness. When their spaceship got stranded on Earth they kidnapped and tried to use Tempest as a mystical power source.
Their plans where thwarted by Aquaman.
Later, after their defeat, Tempest provided the energy they required to start their spaceship, and they departed Earth.
Powers & Abilities
The Omniguard could fuse in a single very powerful form or multiple less powerful copies. Omniguard's powers included:
Superhuman Strength: Enough to fight Aquaman and Tempest.
Superhuman Durability: Able to withstand Tempest's energy attacks and Aquaman's harpoon slashing had no effect.
Eye Beams: Omniguard could discharge powerful beams through it's "eyes"
Duplication: Omniguard could separate into different copies, with different powers.
Elasticity: One of the copies could elongate similar to Plastic Man.
Ice Blast: One of the copies could project ice through it's hands.
Telepathy: Omniguard used some sort of mental power to create an illusion and disguise their hiding place.