Let's think about some historical examples: Renewed Faith was cool because you rarely played it
This card wouldve been terrible even if it werent for its cumulative upkeep, which means you have to pay 1 more mana each turn to keep this already awful charade going
Generals of Primal Genesis In the Populate deck, Primal Genesis, our marquee legend is Ghired, Conclave Exile, who reminds me of how I wish I had done some exploration of Populate in the last seven years, but with Ghired, I absolutely think I can make up for lost time
This mechanic was very much liked, and there are a lot of werewolf fans
And thats not even really mentioning the once in a Pokemon era chase that the Umbreon ex SIR certainly is
(You expend 4 as you spend your fourth total mana to cast spells during a turn.) Whenever you expend 8, exile the top two cards of your library