What ancient Greek historian wrote about the Peloponnesian War?

Thucydides

In the "Kingdom Hearts" series, who is the main protagonist wielding the Keyblade? Who was Poe Dameron's droid companion? Corsica is a part of which European country? Which creature from Elder Scrolls III: Morrowind serves as a primary means of transportation around Vvardenfell island? Who created the notation 'f(x)' for a function?