Is it broken as is? I hope not.

Pretty broken, seeing that it can be turned on by Scalding Tarn.

Forbidden should cost more than the regular cost. Also shouldn't be a mechanic at all: it leads to repetitive gameplay and is a logistical nightmare.

Welll... it's only gonna trigger while you're searching; so you need to add on the cost of the tutor you're using. Which is, at minimum, a card and .

On the flip side; though; you don't give up the normal tutor; so it's just an opportunity cost.

So this is kind of "Splice - tutor" which is interestingly powerful to say the least. But yeah; it would be very repetitive.

­ and a card? If only. No, as jmg says, this will mainly be triggered by Scalding Tarn and Terramorphic Expanse and so on. I do like the Panglacial Wurm ability, but it does have developmental problems.

Also want to point this out: http://magicjudge.tumblr.com/post/93628251814/im-actually-kind-of-upset-by-your-last-answer-to

Agh, headache It sounds like abilities which do anything irreversible should not be mana abilities, and Sevala is a case they haven't caught up with yet.

I don't think Panglacial Worm is broken, but I agree it's treading in dangerous waters...

I raise you Chromatic Sphere/Chromatic Star. Wizards knows it's an issue and printed Selvala anyway. I'm pretty sure Tabak had mentioned how awful Panglacial Wurm is as well.

thinks ok, maybe it's a bad idea...

I was quite annoyed at how cavalier Tabak's attitude to the assorted Selvala problems was. It could all be fixed by just decreeing her ability to not be a mana ability, or giving it "Activate only any time you could cast an instant" errata like Charmed Pendant.