Selvala, Heart of the Wilds does not have summoning sickness.
Notable Prerequisites
You have a way to give
Selvala vigilance.
You control a creature with power 6 or greater.
Mana Needed
({G} magic symbol) available.
Steps
Declare
Selvala as an attacker.
Holding priority, activate
Selvala by paying ({G} magic symbol) and tapping it, adding at least ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Activate
Najeela by paying ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) , untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.