One of the original sins of Commander, Crypt was deemed legal from the format's onset, despite being clearly overpowered relative to most other mana accelerants
Enchanted creature gets +1/+1 and has "Whenever this creature attacks, scry 1.") At the beginning of combat on your turn, you may pay
It could be argued that this is still the most elusive and sought after Charizard in the Sun & Moon series (yes, even over the Hidden Fates one)
It has ninjutsu for one black mana and three generic mana, and, when it deals combat damage to a player, you exile the top card of each player's library
While players can brew and build decks featuring Radiant Lotus, theres no telling how the metagame will react
Lead Developer Mike Turian chose to break a design principle by introducing the zero loyalty cost via Jaces Brainstorm ability and still allowed Jace to protect himself through a minus ability that negated threats that didnt come with haste