'Tis the Monado. Instrument of destruction and rebirth.
Specifically, it's one of three Monados in the game. That is Zanza's own Monado, but is the one Shulk uses throughout the game, though it changes form when Zanza first appears in the game in his true form. In that form, it's the tool Zanza uses to fight Shulk (who at first has a replica Monado before summoning his own) and is what he uses to destroy the world and create a new one.
The symbol (which is Japanese) that appears in the centre shows what power the Monado has at the moment, usually "Machine", "Person" and eventually "God". Those symbols show what type of creature the Monado is capable of harming. Other symbols like "Enchant" or "Speed" are used to grant other party members the temporary ability to harm Mechon and gives one party member a temporary evasion boost, respectively.
Look... just watch these 3 and hopefully you'll get it.
(Or at least see the Monado in action.
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