How can you call it "cheap cost"? Thorn Shield = 7
-- one time. Wand of Tartarus = 4
up front, plus 4 plus 2
EVERY TURN. That's 3 more quanta for a
single use, plus 6 more every turn you want to use it in the future. And that's
upgraded, versus an unupgraded Thorn Carapace.
It practically demands the 2 damage per turn from the Weapon aspect just to make it valuable enough to use.