The ablative case can have many translations but the most common options are by, with, from, in or on.
1. The ablative case is used with prepositions meaning 'going away from':
cives qui ex ampitheatro festinaverunt nunc in foro sunt. The citizens who hurried out of the ampitheatre are now in the forum.
2. Agent and Instrument: The agent (the person or thing by whom an action is done) uses a/ab and the ablative. The instrument (the thing with which the action is done) uses th ablative alone:
imperator gladio necatus est a custode…