This pair of lands became infamous in the game's early years
self-discard often involves lots of rummaging and looting to filter through your deck, giving you plenty of time to find the perfect answer and keep the game going until you dig towards you win conditions
Individual bending abilities like Waterbend, Earthbend, Firebend, and Airbend can work outside the set, sure but Avatar Aang himself becomes much harder to build around effectively, especially if your goal is flipping him consistently
Consider how strong this thing is in the set after Blood tokens were introduced
For Modern Horizons 3 , a Historic supplemental set, a different player reward system dubbed the "Horizon Hideaway" was opened, running concurrently with the Outlaws of Thunder Junction track