I'm going toplace a bet on Vlaakith being the Absolute.
We know she's plotting to ascend to godhood from lichdom, she's been putting her needs ahead of the Gith purpose for centuries already, this could be her endgame.
The artifact could be her phylactory or something of that sort. Semi-sentient and containing much of her pre-lich personality and ambition - lead the Githyanki to victory over the mind-flayers. It is opposing Vlaakith, and doesn't want to fall into her hands via the Gith who have been sent out hunting the "weapon", or the cultists.
Vlaakith has fought Illithids for a long time and probably understands them very well. Discovering and manipulating an Illithid plot to her benefit instead of destroying it would be risky, but if the reward is tricking her ancient enemies into helping her ascend, it would be tempting.
Remember when Lazy talks about the K'lirr library? Vlaakith is smart and extremly well informed about every race religion and organisation, powerful in her own self and with forces to command and with a racial portfolio there for the taking, she's halfway there already.
