On one card
They are designed for Limited formats, give every player a fair card pool, and keep the opening experience exciting with foils, wildcard slots, and chances at extra rares
If so, how many, and which ones
It's a great mana dork in Eternal formats filled with fetch lands, but the activated abilities are also incredibly powerful
Due to Universes Beyond and Secret Lair drops, theres increased scrutiny in how successful the marriage of theme and mechanics is, each wave judged on how well it can balance these facets with different standards depending on how rusted on or competitive a player the individual is
Sudden Chill is more of a control card to remove one of the opponents Characters from play and slow down their pace immensely