Battle for Baldurs Gate is ideal for this, as it has an open-ended deckbuilding mechanic in the Choose a Background mechanic
But at the same time, Ive accumulated single copies of some really good blue spells for the time when I wanted to play on the dark side: I just recently traded for a Mana Drain, a card Ive secretly coveted for over twenty years, but thanks to a reprint I was able to pick up an Iconic Masters copy for a reasonable exchange
You'll still discard a card as an additional cost to cast it
Most Commander games are going to be done before Turn 22, so I dont think we need to worry about that
Building a heroes deck in this set means I'm running nearly every Spider-Man legend I opened, with the exception of Anti-Venom, Horrifying Healer, which has a casting cost of five White mana
That does not mean this card is bad, for it is quite good