It is intended to be played by two players who each take two of the mono-colored decks and shuffle them together, creating two 60-card, two-color decks, and will release in local game stores, mass market stores, and online stores on Leap Day, February 29, 2020
And notice that the only once each turn restriction means you can trigger it on your opponents' turns.Terrasymbiosis plays particularly well with earthbend, and it's often played in the 99 when Toph, the First Metalbender is in the command zone
Those strategies are cards that gain value from discarding (especially lands), cards that can allow you to play many lands, landfall, and cards with leaves the graveyard triggers
Much like Vindicate the strength of Counterspell is due to the broad range it has however its effectiveness is entirely based on how you use it
Counters, planeswalkers, experience, poison - Kilo enhances all of them