Toph, Hardheaded Teacher

Earthbend converts casting into board presence sideways, animating a land and stacking counters on it, but the interesting choice is which trigger the mechanic hangs from. Casting any spell earthbends a land, and Lessons add a second counter, so the reward compounds with how many spells you chain in a turn rather than with the size of any one of them. That is a deliberate rate. No single cast produces a threat, but the counters pile onto something carrying haste and an insurance clause: an earthbent land killed off is not gone, it comes back tapped and ready to grow again. The animated lands are still lands, which turns removal into a partial answer at best, since destroying the creature only leaves you with a spent mana source. The enter trigger, discarding to buy back an instant or sorcery, keeps that engine fed by recurring the very spells that keep earthbend firing, though it costs a card to do so and reaches only instants and sorceries. Toph asks a spellslinger deck to treat its mana base as the accumulator, growing lands into a threat instead of drawing one. The stats matter least here; the design pressure sits entirely on velocity, on a build that would rather cast four cheap spells than one expensive one.