This Magic the Gathering card combo covers Gilder Bairn and Primordial Hydra.
Primordial Hydra gets really big, really fast, if he stays out long enough. Why not speed his growth along with Eventide’s Ouphe extraordinaire, Gilder Bairn?
Here’s how it works:
Cast your Gilder Bairn, and then cast your Primordial Hydra for as many counters as you can on your next turn. Attack with Gilder Bairn (or find another way to tap him), and then use his untap ability to double your Hydra’s counters. During your next upkeep, that number doubles again, and by now he also likely has Trample. Keep in mind that Gilder Bairn’s ability can also be used during combat, so if they are attacking together, you can untap Gilder to double the Hydra’s counters again.
This combo also works well with Zendikar’s Scute Mob. Note that these three cards are a nice fit for your deck’s mana curve. It’s even nicer with cards that accelerate your land drops like Harrow, Cultivate, and Primeval Titan.