Titan's Presence

The additional cost solves the whole engineering problem in a single line: removal that scales with the size of your threats, but only your colorless ones. Colorless creature decks were always long on raw size and short on interaction, since their payoffs lived outside the color pie that hands out clean removal. Revealing an Eldrazi to exile something converts the deck's defining strength (it plays enormous, often colorless bodies) into a mode of answering rather than only attacking. The reveal is the price that keeps the spell honest: you pay no mana for the card you show, but you must already be holding a colorless creature large enough to outsize the target, so the spell answers only as well as the hand behind it will allow. Exile rather than destruction is the correct finish here, since the fatties this deck most wants gone tend to crawl back when merely killed. It is narrow by design, near-dead in a deck running no colorless creatures, and the constraint doubles as the thesis: the card does nothing until you have built the tribe it serves, then repays that investment with interaction the archetype otherwise could not touch.