Ashaya, Soul of the Wild
The clever trick here is a type-line rewrite, not a keyword. By turning every nontoken creature you control into a Forest, this animates your board into ramp: each creature now taps for green through any effect that untaps or exploits lands, and each one counts toward Ashaya's own body, which scales off lands you control. The synergy that defines the card is with untappers, and specifically with creatures that generate mana or activate off tapping for mana. A mana dork that becomes a Forest can be untapped by an effect that untaps a Forest, which is how the card slots into infinite-mana engines rather than just a big-green midrange plan. The nontoken clause is the balancing line: tokens stay tokens, so the effect rewards a board of real permanents rather than a swarm you spat out with one spell. There is a second edge worth naming: making your creatures lands also makes them vulnerable to Armageddon-style land destruction and to nonbasic-land hate, and it means a single sweeper aimed at lands can catch your creatures too. The reminder text preserves summoning sickness, so these newly-minted Forests cannot tap the turn they arrive unless they already could. It is a rare design that hands you a board-wide land-type stapling and asks you to find the untap effect that breaks it.
