As the name suggests, the first print run of Japanese Base Set cards didnt include a rarity symbol in the bottom right hand corner
If you want to get really spicy, add regional variants so that they can adapt to the environment they're in
It ceases to exist as a state-based action
That goes very well with cards like Laelia, the Blade Reforged, or Prosper, Tome-Bound if youre branching into other colors
You may cast it and never level it up, or you may wind up grinding it all the way to to level 3 over the course of the game
Each of these legendary artifacts discounts spells of the relevant color, provides a useful passive ability, and has an activated ability that synergizes with its passive ability