The latter included ancient wooden tablets covered with an unknown form of writing.

After a nuclear power plant in Mississippi explodes, it's soon realized that a previously unknown form of radiation is released.

Or was it a planet in some unknown form?

The remaining 70% is an unknown form of energy - dark energy.

Lucifer used a ray gun firing unknown forms of destructive energy.

But he could also assume other forms, unknown to his parents.

It's stated to contain some mass in an unknown form, which is used when someone morphs into an animal bigger than their own body.

"It is a completely unknown form of life," Riker argued.

It shows a porous form of bronze, virtually unknown for that period, and museum officials say the cat is probably a fake.

Gatecrasher usually wears wrist-blasters that fire an unknown form of energy.