For three mana, you decide how much life to pay and shrink every creature accordingly
Twenty basic lands is a curiously high number for a three-color deck, especially when there are plenty of cheap non-basic lands that could help here (some of which are even in Modern Horizons 3)
You can then tap the Crucible and remove storage counters to gain that much mana in any combination of colors - solely for casting Dragon spells or activating Dragon abilities
Not only does this remove a threat from play for at least one turn, but it allows you to play an extra, high-cost card and potentially close the gap between you and an opponent
There's no doubt that this will remain one of the best Gengar cards ever, judging by art alone.
Really liked seeing some small re-balancing to the game as the result of ContentlyForlorn's changes on various cards (switching around attacks, damage, HP values, etc.)