Zeus is a thundercloud homie created and formerly owned by Big Mom, that she summoned from her left hand. It is a special kind of homie, as it received a soul fragment from Big Mom herself.
During the escape from Totto Land, Zeus was captured by the Straw Hat Pirates and forced to become Nami’s slave. However, it has seemingly accepted its new role, as it now lives inside her Clima-Tact. As a result of this, he has effectively become Nami’s newest weapon.
Zeus is far more powerful than normal homies, being made from a fragment of Big Mom’s very own soul. This gives the cloud a will strong enough to resist the soul projection of the Yomi Yomi no Mi’s user. As a cloud, Zeus can fly, produce both normal and “sweetened rain” and attack with powerful bolts of lightning strong enough to defeat Vinsmoke Judge in one hit. Now Nami can use Zeus supplemented with her Clima Tact abilities to perform destructive lightning attacks.
Zeus can also expand and serve as a seat for the user, being made of more dense and tangible material similar to Sea Clouds, and can carry objects and people while flying. It can fly at incredible speeds, enough to catch up to the Straw Hats, who had a significant headstart, while carrying Big Mom.
Nami is already a smart woman, capable of manipulating the weather to a great degree. With Zeus, she’s going to be a truly fearsome opponent!