>>14432434Mecha Bee is Calamity boss unless you mean Mothra, but seeing that you've already acquired True Excallibur, that means you have already killed at least one of them during Solar Eclipse.
Next stop would be heading to the jungle, drilling green ore and looking for a shiny bulb that spawns Plantera upon being destroyed.
Make a big arena around it and if you fail, you will have to find another bulb and place a bed in arena, so that you can tp to it with mirror after destroying the bulb, no matter how far it could be.
