Can you use a replacement effect to replace drawing a card with a different effect even if your library is empty?

A replacement effect that modifies or replaces the act of drawing a card applies before the draw actually happens. Under CR 616.1 and CR 120.1, drawing a card is a defined event, and replacement effects (CR 614.1) intercept that event and substitute a different one instead of letting the original occur.

Crucially, the replacement effect applies regardless of whether there are cards in your library. The original draw event is replaced before the game even checks whether a card is available to be drawn. This means you never reach the state-based action (CR 704.5b) that would cause you to lose the game for drawing from an empty library — the draw simply never happens.

A classic example is Teferi's Puzzle Box or, more directly, Obstinate Familiar-style effects. The clearest illustration: if you have Reminisce-like setup and an empty library, an effect like Multani, Maro-Sorcerer's isn't relevant — but if you control Abundance (which replaces a draw with revealing cards until you find a land or nonland), activating Abundance's replacement means you never actually 'draw,' so an empty library does not cause you to lose at that moment.

Under CR 614.1a, replacement effects replace an event with a different event. Once replaced, the original event (drawing from an empty library) never occurs, so the losing condition of CR 704.5b is never triggered by that action.

Important condition: The replacement effect must fully replace the draw. If it only modifies the draw (e.g., 'draw two cards instead of one'), you are still drawing, and an empty library would still kill you for each card you cannot draw (CR 120.3).