Once Platypus-Bear has attacked, it will remain an attacking creature for that combat, even if the Lesson card is removed from your graveyard
It should go down even further, but the bottom price could be somewhere around $7-10, and that's something one should not overlook
This simple-seeming card has multiple roles
Esper Control is probably the third most-popular deck in the format right now, but is Chromium likely to be more of a mirror-breaker in the sideboard, or a versatile maindeck threat
1x Double- or single-faced rare or mythic rare 1x Double- or single-faced uncommon 1x Double-faced common 2x Single-faced uncommons 9x Single-faced commons 1x Eternal night basic land 1x Double-faced helper card 1x Token or ad card COLLECTOR BOOSTERS If you want a straight line right to the sharpest, most vicious cards in the set, Collector Boosters are for you
For Constructed Magic, though, that darn if you play a card, bury Juju Bubble clause is a huge dealbreaker