These three cards all control your opponents tapping/untapping so they already have mechanic synergy
Then the pump ability gives you a mana-efficient way to use your mana for extra damage every turn
Legendary Creature - Rogue Aetherborn Color tag templates(None) Halo Forager Flying When this creature enters, you may pay
There is a chance that Ultima is too slow against Prowess, but if control decks can construct themselves to routinely survive until turn five, Ultima blows them out
From this perspective, you should buy every Secret Lair drop, whether you actually want it or not, knowing that you'll basically break even most of the time, while not-that-infrequently, you'll hit an above-average drop and double your money
That means you are not splashing that effect unless it is good enough for a real commitment to the color or lack thereof, just like how splashing Treetop Village is often not the best idea (but not always!)