Antonyms for the phrase "climbed up on" could include words such as descended from, went down, descended upon, or descended into. These words suggest a downward movement or a movement into a lower position, rather than an upward one. Other antonyms could include words such as settled into, sat down, stayed put, or remained stationary. These words suggest a lack of movement or a position of stability, rather than the action of climbing up. Overall, there are many different antonyms for the phrase "climbed up on," depending on the context and the specific meaning that is being conveyed.