On Venat's Role in the Story

[pinkbubblegum]

Again, Hydaelyn couldn't have possibly known that part through any kind of foreknowledge; she was just smart enough to realize that such a gift might be essential. I don't think she actually foresaw that reviving the Drama Club Boys would be a key element, she just trusted that, if given all the tools we could reach, we'd find our way. ...because frankly if we didn't, everyone was screwed, so let's hope this one basket we're putting all our eggs in pays off.

I mean, I agree with you haha. She shouldn't have known yet Hades' line implies she had definitely considered the scenario xD
Hydaelyn truly knows and conceives of all www

The ability to make Hades and Hythlodaeus alive again/manifest is literally describing Hydaelyn's power to "to give form to the formless" which is the gift Hydaelyn said she was giving the Azem crystal the ability to use for a short time, there's no need to come up with a new unknown bonus gift, Azem's standard regular invocation is the ability to summon souls to their aide (like how we did with Emet-Selch in 5.3), but it's is Hydaelyn's power to give them matter and form.

And the WoL knew they couldn't revive the Scions until they figured out a way for Ultima Thule's existence to longer require the Scions souls keeping it survivable/no long in a state of Terminus, so they summoned/revived Emet-Selch and Hythlodaeus first because the WoL realized their creation magicks would be able to accomplish that and thus make the Scions souls no longer necessary to survive/forge ahead.

I just rewatched the CS and you're right. Hythlodaeus even says it was WoL that called the two of them, so it was definitely the crystal having enough power for both of these acts.