The Citadel of Chaos

You turn the handle as carefully as possible so as to surprise whatever awaits you.
Slowly, the door opens and you enter the room, which is dark and lit by a single flickering candle.
Your blood drains as you see a three-pronged TRIDENT heading directly for your throat!
In a flash you must decide what to do.

Will you:

Immediately cast a Shielding Spell ?

Try quickly to side-step the weapon ?