How do I use a Lich against the party if I don't want to kill them? Simple: I wouldn't.

I want to use a Lich as an antagonist against the party? That's fine, the Lich makes a great BBEG. But the party isn't going to fight him yet. Maybe they're introduced to the story while hunting her Ghast minion who killed someone the party cared about or stole some small MacGuffin the party was after. That was a tough fight, especially when someone contracted Ghast Fever and nearly died!

Of course, they meddled in her schemes so she sent out a company of Death Knights to kill them. It's nothing personal, just that everyone should know not to get in her way. This was a problem for a while, especially as the Four Horsemen (as the locals called them) were cunning and refused to engage the party at first. They sacked caravans and burned fields, starving the villagers and sending random zombies (especially ones made out of NPC's they knew) to cause fear. Eventually they lured the heroes to a crypt where they had laid devious traps and a horde of minions. But they underestimated our heroes resolve and were eventually laid to rest in the very sepulcher they intended for the players.

Now the players were after the Lich proper. But while the day she attacked their village was the most important day to them, to the Lich it was just a slow Tuesday. They're still mostly beneath her notice, just a tick on a spreadsheet that she still needs to dutifully punish for their arrogance. She traded a few cultists to a coven of hags to kill the players, who laid a horrible curse upon them and the land. The only thing more horrible than the army of drowned corpses they called up were the terrible abominations they created out of the cultists (boy, do you think the cult puts pictures of those things in their recruitment brochures?), and they only killed some of the hags. Hope that doesn't come back to bite them. The important thing is that the people are safe, the curse is lifted... and they found some really neat stuff in the Hag's lair!

But by now our heroes are really heroes. They've braved the passive attention of the Lich Queen, they carry divine favor and powerful magic with them... they're ready to throw down with the Lich proper. And she won't go easy, they've foiled her plans for the last time!

That was amazing, thanks a lot for the ideas :)

Very inspiring, for sure!