Grand Entryway // Elegant Rotunda

The Room design splits one card slot into two effects you buy separately, and this pair leans into the split rather than fighting it. Cast Grand Entryway for and the Glimmer token arrives now; Elegant Rotunda stays locked on the battlefield until you pay at sorcery speed to unlock it, at which point up to two creatures each take a +1/+1 counter. The two halves are written to feed one another: the token from the first door is a legitimate recipient for one of the counters from the second, so the card reads as a compressed curve (make a body, then grow it) instead of two unrelated effects sharing cardboard. What paces the value is that unlocking is a sorcery-speed action and each door pays out exactly once. There is no instant-speed ambush and no loop; you unlock the second door on a main phase when you have the mana free, not by leaving mana open across turns for interaction. The Room structure is really the point here: it lets a deck commit the cheap front half early and bank the counter payoff as an upgrade it already owns, cashing it in when the board is worth cashing it in on.