Larian Studios Forums Baldur's Gate III Baldur's Gate III - Story & Character Discussion The artifact and the Sussur bark

While being called an artifact, its just a portal. And portals are closed withing antimagic fields, like what the sussur bark projects.
And even if the portal is left open, antimagic also blocks ilithid psionics.

So how is Tav still alive after picking up the bark?

Seek not reason where there is none.
This antimagic field does not prevent the crazy Drow from casting Sheild ...

So I would say that the problem here is that antimagic shouldn't block psionics in the first place. They're specfically different from standard magic so should have a different effect. If you really want a justification, you could say that the level of magic being used is strong enough to overwhelm the resistance of the sussur bark, I guess.