The witch is indeed a rather terrifying creature.
The Undead Tribe has never before found themselves in such a hard battle on Toril... Of course, it's not that they haven't encountered powerful beings capable of annihilating their group in the past, but at those times, the figures of other deities would always appear to stand in their way.
And enemies with equal combat power on Toril simply can't withstand the numbers of the Undead Tribe.
So, this is their first time in such a difficult battle... The so-called Witch Gathering means that when they number more than three, they form a formation, creating a resonance.
An adventure party without a Transcendent, even if their level is not low, always ends up wiped out when encountering three witches.
In many adventure stories, including various Paths of Destiny, the outcome of encountering a Witch Gathering is either to flee, or to sacrifice a few companions.
