Shouldn't his ability be technically called 'Rebuilding'?
Interesting idea, but what would happen if the pillars this guy targeted were completely destroyed? (say, by an Earthquake first round) What would happen if you targeted an enemy's pillar?
I called it 'Reclaiming' because it makes unused power useful. And wouldn't 'Rebuilding' need something destroyed.
To the questions:
1) The pillar would be produced even you lost all targeted pillars because you only need the pillars to define the element.
2) The player with the Cultist gets the pillar and not the player with the targeted pillar. And you can target your opponents pillars.
Love the idea. Not sure if Earth is the element that needs this as its the only element that can actually protect their pillars. 
I'd love to see this as "other" element card though as it would open lots of different strategies for non-mono decks.
Also, I'd make it with 0 attack stat (though, this guy will probably be building pillars 24/7, so not attacking anyway).
The card should be affected by damage shields when it doesn't use the ability.
And I think that this card fits earth. The other thing is that making the card from the element 'Other' would destroy the balance of the card and the Traveling Cultist (
http://elementscommunity.org/forum/index.php/topic,7195.0.html) can gain the ability as 'Other' creature.
