The value of X is calculated only once, as Siegfried's last ability resolves
Murderous Redcap for instance can ping your opponents to death, while Puppeteer Clique can empty their graveyards, temporarily giving you all their creatures, and activating Celes' ability at the same time
Use this to your advantage while trying to quest with Nala safely
If you care about tournament play, which many players simply dont, the question becomes if Izzet Cauldron will get so unsustainably dominant that it pushes out other decks from play, and if thats a fun format to play in
The Timeless Wisdom precon comes with some powerful cards that I've kept in the mix
With a relatively accessible Station requirement of (8), it should be trivial to get your win condition online