When Void Hatchling's replacement effect interacts with Rek'Sai's legend ability (which reveals the top 2 cards), does it let you look at an extra card, and can multiple Void Hatchlings stack?

Ruling: Void Hatchling's replacement effect changes Rek'Sai's "reveal top 2 cards" into "look at the top card, optionally recycle it, then reveal top 2 cards." If you recycle the looked-at card, you effectively see 3 total cards (1 looked at and recycled, then 2 revealed). If you don't recycle it, it becomes the first of the 2 revealed cards.

Sequence: (with one Void Hatchling)

• Look at the top card of your deck
• Choose whether to recycle it
• If recycled: reveal the top 2 cards (which are now different cards)
• If not recycled: that card becomes the first of the 2 revealed cards

Sequence: (with two Void Hatchlings)

• Both replacement effects apply to the same "reveal 2" event
• First Hatchling replaces it with "look at 1, then reveal 2"
• Second Hatchling replaces the "reveal 2" within that effect, nesting as "look at 1, then (look at 1, then reveal 2)"
• Result: look at top card (may recycle), look at next top card (may recycle), then reveal top 2 cards

Nuances:

• Multiple Void Hatchlings do stack because each replacement effect can apply to the "reveal" portion that remains in the modified effect
• These are passive replacement effects, not triggers, so they layer and nest rather than going on the stack
• The second Hatchling specifically replaces the "reveal" portion at the end of the first Hatchling's modified effect