The phrase "art at daggers with" implies a situation where two things are in fierce conflict or opposition to each other. Antonyms for this phrase could include "in harmony," "in agreement," "in synchrony," or "in unity." These antonyms denote a sense of cooperation and mutual understanding between two entities. Alternatively, antonyms for "art at daggers with" could also be "negotiated," "resolved," "settled," or "concluded," indicating an end to the conflict and a move towards finding common ground or a compromise. Ultimately, using the right antonym for "art at daggers with" depends on the context and the nature of the situation at hand.