Nature is very powerful :
forest defense : not always useful, but manytime, having a defender in your stack that has +25% defense just for a measly adept spell is poweful.
poison blade :
-is a given for ranger-beastmaster, assasins, shadows (+1

, it's powerful)
-is also mandatory if you play FOL : fawns and satyr are quite cheap units, for their power.
-beastmasters are one of the more powerful units ingame, no weapon promo so not liable to rust nor weak to lignthing damage, no promotion against recon units...(especially for rasing stacks out of cities) so poison blade is very interesting to have, as much as enchantement.
vitalise : very powerful, but less useful as demanding a lot of micro. genesis works once, vitalise can bring tundras/floodplains into grasslands, not just into plains !!
I agree that vitalize can be done (almost) with genesis, but poison blade is soooo..