Did Rei need Adam's embryo to merge with Lilith's body?

[extherian]

So after her rebirth in episode 23, Rei not only has her complete soul back but can also generate AT fields as seen in episode 24 when she appears in Terminal Dogma. And she can apparently dissolve her own AT field to merge with the bodies of others, as she does in End of Evangelion to absorb Adam's embryo from Gendo's arm.

What is not clear to me is why she needs Adam's embryo to return to her original gigantic form as Lilith. If Lilith as it lies on the cross is her original body, what is to stop her from merging with it any time from episode 24 onwards, Adam or no Adam? Would she just turn into a giant but without the ability to start Third impact? Would nothing happen at all?

[Axx°N N.]

Various different versions of 3I, involving Rei or otherwise, operate as the endings for the Evangelion game that the CI lore details come from: thread/8742/NGE2-Alternate-Outcome-Translations-3I-Etc/

There are scenarios where only Kaworu fuses with Lilith, and various ways we see Rei interact.

It's the closest answer to your question that exists in official media, but its canonicity should still be taken for what it is; a game written not by Gainax, but with classified series bible details shared by Gainax. There's no way to really know what Anno or other writers would say is totally lore accurate, or at least as credible as those events in the show itself.

[thewayneiac]

She doesn't need it to merge with Lilith; she needs it to bring about the forbidden union of the two fruits to cause third impact.