Found a way through the ruined cistern.

Escaped a cage in the Arsenal without setting off a grenade.

Found an unfinished letter from an archaeologist to his sister.

Get a 500 Hits Combo

Kill the Colossus of Rhodes, the Dark Rider, and Theseus

Power up any item

Defeat the Dark Rider for the first time

Followed the pilgrim's trail to take refuge in the fort.

Climb from the pit of Hades

Dreamed of Paris.

See the true ending

Kill up to 50 frogs (accumulative)

Unlock the frog-hat