|A lich who, having existed for countless centuries, has grown almost unimaginably powerful through the study of dark magic.|
Ancient liches are extremely powerful undead casters with a wide array of resistances and access to several deadly attack spells that can deal ridiculous amounts of damage or summon devastatingly powerful allies. If you are not confident in your skills, escape is strongly advised. Ancient liches can rarely be found on the last floor of the Vaults, in the Abyss, the Crypt, the Tomb, and the Realm of Zot, and are a common sight near the orb chamber of Zot:5.
Tips & Tricks
First and foremost, understand that ancient liches are some of the most powerful casters in the game. Don't worry too much about conserving resources; if burning a consumable or two will greatly ease the battle, do so.Berserking is chancey, as ancient liches often generate in places where you don't want to be attracting a lot of attention, but the boost to HP and damage can make a huge difference.
As liches resist most elemental damage, combat casters should rely on pure Conjurations or Earth Magic. Necromancy specialists can deal brutal amounts of damage with Dispel Undead, though it requires getting to and staying in point-blank range. Nearly all Hexes are useless against their infinite willpower, so don't bother with them.
Melee fighters should lure them around corners or use scrolls of blinking to get into melee range as quickly as possible; lest you get pounded by brutal attack spells or face dangerous summons. Once there, casting Silence or reading a scroll of silence will disable the vast majority of their abilities. It may be worth swapping to a Holy wrath- or antimagic-branded weapon, if avaiable. The lich's melee attacks might not be insignificant, but they're a good deal safer than most of their attack spells.
Throwing nets are very useful against ancient liches. Throwing a net at the edge of LOS guarantees that the lich won't be able to follow you for several turns, allowing a fairly safe escape. Nets distract monsters; letting any player, especially Short Blades users, multiple chances to attack for free.
Of course, since it's unlikely that you'll be able to take them out without taking a single hit, being able to survive their spells is advisable. Don't go after them while wounded, apply any useful buffs you may have available, and consider chugging a potion of resistance to patch up vulnerabilities; it may be wasteful, but better to be safe than sorry! Taking 100+ damage in a single turn stings.
As always, remember that killing a summoner destroys all its summons. If you are confident you can finish off an ancient lich before its summoned fiends can tear you to pieces, go for it. If you aren't confident of that, consider what safe escape routes you have available.