Serpents leave their eggs in the cold and inky depths...

Biolume Egg

Defender
When Biolume Egg enters the battlefield, scry 2.
When you sacrifice Biolume Egg, return it to the battlefield transformed under its owner's control at the beginning of the next end step.

...knowing their hatchlings are more fearsome than anything else that might come along.

Biolume Serpent

Sacrifice two Islands: Biolume Serpent can't be blocked this turn.

Biolume Egg // Biolume Serpent

Defender
When Biolume Egg enters the battlefield, scry 2.
When you sacrifice Biolume Egg, return it to the battlefield transformed under its owner's control at the beginning of the next end step. 

 Sacrifice two Islands: Biolume Serpent can't be blocked this turn.

Biolume Egg // Biolume Serpent

Creature — Serpent Egg // Creature — Serpent