Fighting a lich is not something one does lightly.

Jubilost keeps arguing that maybe they shouldn't try it at all, it's not like it's good for their lifespans or their souls, but - Sivetrys can't, actually, just leave it alone.

(Technically, she could, but. Emotionally, she can't.)

There are a lot of reasons for this. The ones she uses first are the logical ones, but she's aware that's not really why she can't leave the lich alone. It's just why she can justify the choices she already wanted to make, to herself, to her adventuring party (friends), to fucking Lastwall itself.

Vordakai is an old lich, which usually means extremely dangerous, but in this case it means he's, technically, changed species. A demilich is different from a lich in several ways - in a couple, more directly dangerous - but in others, it is much, much easier to deal with. He's lost circles, for one. For another, it means that they don't have to find his phylactery; he doesn't have one of those, anymore. The process for permanently killing him is still complicated - and Sivetrys has written to Lastwall for assistance on the logistical details of making that death final, along with asking them to please send her a paladin - but not as complicated as hunting down a phylactery in a demiplane underneath several dozen protections.

Secondly, because he is an old (demi)lich, from before Earthfall, his spells are out of date. Oh, he still has some dangerous ones, Dominate Person is a sure one they've confirmed, and her party is systematically trying to put a list together of what those are, but he's missing modern ways to reduce the circles of certain spells. His spells are old and inefficient, and in life and undeath he was never able to competently steal the greatest spells from the Azlanti Empire, else he wouldn't have hidden underground at all. With his demotion to demilich, and the loss in circles that came with that - he can't quite cast his worst spells, anymore. And he doesn't know what modern spellforms are like. Because there has been a steady march of progress, despite Earthfall, entirely because of Aroden's efforts, and all the genius casters after him that really want that high circle spell nownownow.

But of course, this also means that it's a race against time. He is awake, now, and has been since his tomb was disturbed, and some nebulous trinket stolen, and he is learning quickly. There's no mighty Azlant to throw back his own thievery, just these pathetic shreds of what remains after Earthfall. He's already captured one wizard, a third circle one, and he is definitely looking for more. For their spellbooks, for new slaves in his 'justified' rise against the thieves who disturbed him, for their new magical items.

There is no better time to fight him than right now, now that he's awake and actively scheming. The closest people that can maybe win in a fight him are - well, her, and her party. At least, they're the only ones who might, who also care enough to show up. The world is very big, and very dangerous, and liches do tend to stop, after a while. Reach their old borders, sate the atrophied greeds they'd had as mortals, gather enough undead slaves that gathering more becomes tiresome. As dangers on this planet that holds Rovagug go, they're not, objectively speaking, the worst.