It's the vaccine for the release of General Zod.
The tension heightens as elsewhere Lex's body is taken over by Zod who holds Lana captive.
Zod is touched on in the first episode, but only as Major Zod, so this is before he is General Zod.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.