***** Khalni Hydra - If you have plenty of small creatures, then cast this card and slam your opponent

For every green creature you have, this card costs 1 mana less to cast.  I play this in my 2nd Legacy mono green deck.  It works great with small mana boosters like Llanowar Elves, where you can use that card to subtract 2 from this cards cost.  This card is slamming, and I think it will work best in your deck if you are able to play it for less than 6 mana, ideally 4 or 5 mana if you got your game on early and are closing in on a win.