Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Nylea.
When you sacrifice Ordeal of Nylea, search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle your library.
9/15/2013 The +1/+1 counter is put on the creature before blockers are declared and before combat damage is dealt.
9/15/2013 The check of whether the enchanted creature has three or more +1/+1 counters on it happens as part of the resolution of the attack triggered ability. If the third +1/+1 counter is put on the enchanted creature any other way, you won’t sacrifice the Ordeal until the next time the creature attacks.
9/15/2013 If you sacrifice the Ordeal in some other way, its last ability will trigger.