Legends of Runeterra's Content Design Lead has confirmed on Twitter that the Celestial cards you'll see are not completely random.

  • Units will be seen more than Spells.
  • High-cost cards are less frequently seen.

Quote From Shawn Main

Oof. Someone gave you outdated information. Celestials have an individual weighting, but it's not so extreme. Generally, units are a little more frequent than spells and high cost cards are a little less frequent. At the extreme, some celestials are 2x as likely as some others.