Intention: If you let it stand, then it powers up all your tribal walls (which is actually quite scary in the right deck, I may have undercosted this) and animates all walls.

If you kill it once, then all creatures are walls (and that is scary enough in the right deck) - but walls aren't animated any more.

Kill it again to get rid of it completely.

And yes, way undercosted on a rethink - upping it from UW to UW2

I had no idea what "the second effect" referred to until I read your comment. I might suggest templating it as:

Persist.
All creatures have defender.
Creatures with defender may attack as if they didn't have defender as long as ~ doesn't have a -1/-1 counter on it.
If ~ would be countered, instead put it onto the battlefield with a -1/-1 counter on it.

(That's using "Persist" as a shortcut for the reanimate-with-counter-if-no-counter effect, with the slight oddness that you have an enchantment with -1/-1 counters. This works fine, it's just unusual, although not without precedent: Afiya Grove. You could use a more sensible counter type if you spelled out the rules text of persist instead.)

(and Llanowar Reborn)