"Wert on case" is not a single word, but rather a phrase. Therefore, we cannot provide antonyms for it. However, we can provide antonyms for the individual words in the phrase.
The word "wert" is a verb, meaning "were" in archaic or poetic English. Therefore, its antonym would be "was" or "am."
The word "on" is a preposition, indicating a location or relationship. Its antonym would be "off" or "away from."
The word "case" can have multiple meanings, such as a container or a legal matter. Its antonyms would depend on the specific context in which it is being used.