Project Cadmus

"People of National City! The Earth has been stolen from us. The enemy has come in the guise of heroes. They say they come in peace, to protect us from ourselves, but how long will it be before these gods decide to rule instead of serve? We are the antidote to their poison. We are the scientists who will show them what humans are capable of. Those who have sided with the invaders will not be spared. You cannot stop us! We are everywhere! We are Cadmus!"

- Cadmus announce themselves

Project Cadmus is the main antagonistic force in the second season of Supergirl.

Initially a governmental genetic engineering facility, Cadmus cut all ties with the government and went rogue after the proposal of the Alien Amnesty Act. Cadmus has made it its highest priority to eliminate all alien life on Earh, including Supergirl and Superman.

Foreshadowed
When the DEO agent Hank Henshaw is revealed to be the martian J'onn J'onzz, the military sends Colonel James Harper to clean up the DEO. Eventually, Harper orders for J'onzz, as well as his colleague Alex Danvers, to be sent to Cadmus where J'onzz' powers are supposed to be turned into military weapons and Alex will be used in experiments. However, during the transport both are freed by Supergirl and Lucy Lane. Before fleeing, J'onn erases Harper's memory on the events and forces him to resign. From his mind, J'onzz learns that Jeremiah Danvers, father to Alex and adoptive father of Supergirl, is still alive and captive at Cadmus.

Cadmus eventually defects from the DEO and starts working against all alien life on Earth, also cutting all ties with the government.

Metallo
Shortly after the defeat of Non, Cadmus gets hold of some kryptonite from the DEO. They later use this to turn the wounded hitman John Corben into the supervillain Metallo.

After Metallo has been created, Lillian Luthor sends him out to fight Supergirl and Superman. Although Metallo is ultimately defeated, Lillian is pleased as he put up a good fight and even managed to wound Superman. Although her assistant is not happy with Metallo, claiming that he is not ready, Lillian intends to rely on Metallo in the future. Furthermore, she orders her faithless assistant to be turned into a cyborg as well.

Cadmus makes their presence known to the world, hijacking all public broadcasts in National City. Cadmus claims that aliens have taken Earth from the humans and that they have to be eradicated. Cadmus declares war on the aliens and adds that all who protect the aliens will be eliminated as well.

When their assistant-cyborg is completed, Cadmus sends it to Metropolis to wreak havoc. To prevent Superman and Supergirl from interfering, Cadmus sends out Metallo as a distracton. Meanwhile, Alex Danvers uncovers a Cadmus mole in the DEO, the same person who provided Cadmus with the kryptonite. When she tries to apprehend him, however, feigning another kryptonite delivery, the man is shot by Lillian Luthor who arrives with other Cadmus agents. Lillian attempts to convince Alex to join Cadmus but Alex refuses, even admitting that her father is still alive. After Alex' refusal, Lillian orders her men to kill Alex but Alex is able to escape.