Asternove
Retinazer
Currently, Summoner has little to no effective weapons against Plantera. Nothing is obtained after all three mechs, not even an accessory. On the other hand, I believe it has more than enough to tackle Golem with Desert Tiger, Morning Star, Kaleidoscope, the entirety of the Pumpkin Moon, etc. Deadly Sphere staff, although not a bad or useless weapon by any means, could work a lot better as a weapon available alongside the Death Sickle. It would also incentivize redoing the solar eclipse pre-Plantera as well. Of course, it and its respective enemy would need a light nerf to fit progression better, but overall I think it would slot in nicely here.