The exact wording is, " Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn
It could also buy you enough time by unsummoning a full horde of attackers against your slow board, allowing enough time for you to catch-up blockers to your opponent's fast start
Still, being able to mill your library off one card and combo off gives Druid a high enough ceiling that I think merits the number eight spot on this list
If, for any reason, an Aura token that would be created with Arna Kennerd's last ability can't be attached to the appropriate creature, that token isn't created
Honorable Mention #2 - Embercleave This little bad boy is the best of the mythic artifact cycle, to my mind
Flare of Fortitude costs four and your life cannot change and your stuff gets both hexproof and indestructible, normally Green's thing with Heroic Intervention