Ancient Greenwarden is a new elemental creature that really cares about lands in graveyards, and it synergizes perfectly with Nahiri's Lithoforming, another card in Zendikar Rising.
You can use Nahiri's Lithoforming to sacrifice all your lands, draw the corresponding cards, then immediately replay all those lands from your graveyard using Ancient Greenwarden's ability. Doing so will allow you to trigger any card you need on-board twice that many times.
One of the best new solutions for this combo is the Felidar Retreat enchantment, which creates a 2/2 cat token for each land entering the battlefield. You will get two tokens for each land, which could escalate quickly in a proper ramp deck.