If a card says 'draw a card' and another effect replaces that draw, does the replacement effect itself trigger any draw-based abilities?

When a replacement effect modifies or replaces an event, the original event never occurs — only the modified event does. This is the core principle stated in CR 614.1: replacement effects apply to events that would happen and change what actually happens instead. If a draw is fully replaced (e.g., by Teferi's Ageless Insight doubling draws, or Notion Thief redirecting a draw), the analysis depends on what the replacement produces.

If the replacement effect substitutes something entirely different for the draw — for example, an effect that says 'if you would draw a card, instead do nothing' (like a forced skip-draw effect) — then no draw occurs at all, and nothing that triggers on drawing a card will trigger. CR 614.5 confirms the original event is replaced and does not happen.

However, if the replacement effect itself results in one or more cards being drawn (e.g., 'if you would draw a card, draw two cards instead'), those resulting draws DO happen and CAN trigger draw-based abilities, because those are real draw events. The key distinction is whether the replacement produces actual draw events or substitutes something else entirely.

Concrete example: Your opponent controls Narset, Parter of Veils. You cast Brainstorm and would draw three cards. Narset's replacement effect applies — instead of you drawing, your opponent draws one card and you draw nothing. Since you never actually drew, your Psychic Corrosion (which triggers whenever you draw a card) does not trigger for those draws.

So the answer depends on the replacement: if the result contains real draw events, those trigger draw abilities (CR 603.2); if the draw is replaced with a non-draw outcome, no draw-based triggers fire.