Can you burrow opponent creatures? And if so, can they be unburrowed (and does this burrow/unburrow causes a lobotomize)?
If they have an active ability (and any passive apart from airbourne) they keep it.
So no, they cannot unburrow.
Should be same price as nymph, if it can target opponent's creatures. Having the ability to halve your opponent damage is quite strong.
I've increased the cost. Bear in mind that you may have only one of these at a time, unlike the 6 (or more, with PU, fractal, mitosis, etc) you can have of the nmyph. The nymph also does 7 damage as well, so that is why I haven't raised it as high as 8.