First and foremost in five colors: there are very few silver bordered non-basic lands
All these factors make up a rather high price tag for this non-V and non-VMAX card, which is unusual, but not surprising when you consider the power level of the combos
Reen sees all species: chitinous quadrupedal Eumidians, squat tusk-toothed Kavs, gracefully gelatinous Illvoi, even a solitary Drix engineer, slender gray body swathed in billowing mbius strips
You've got yourself a bona fide MTG infinite combo
Having some variance is fine, and even arguably desirable so newer players can have a chance against more experienced ones, but too much is annoying, both for the loser and for the winner (I once played Seismitoad-EX / Giratina-EX and won a series where I hit twelve heads out of thirteen on my various flippy cards
Polymorph When you target your own creatures, Polymorph lets you exchange a creature for another one that resides in your deck