Lith had yet to find a way to raise the Balor's corpse as a lesser undead without the effects of the black eye amplifying the spell and turning the dead monster into a greater undead with a will of its own and a big grudge against him.
Kalla was a much better Necromancers, so her green wisp carried enough of her willpower to harness the full potential of the creature while retaining full control over its ever-growing blood core.
On top of that, Trouble-Kalla shared his thoughts with her original body, keeping the Healers updated about the events unfolding inside the Sapling.
"There's no time to lose, we must go help them!" Marth said once he understood how deep was the Sapling's betrayal.
"You will never make it in time." Trouble-Kalla shook his head. "Dimensional magic is sealed even to those with an acorn. Lyta?"
The Dryad tried to open a Gate leading to the city and failed. She tried several times, changing the destination, but to no avail.