Spell Casting: The lich casts spells like a 13th Level Wizard.
Paralyzing Touch: Any successful attack requires the opponent to attempt a saving throw versus Paralysis, or become paralyzed for 2d4 turns. This paralysis may be cured with cure light wounds.
Cause Fear: A modified version of the reversed spell of Remove Fear, causes ALL target creature within 120’ to become frightened; if the target fails to save versus Death, it flees for 2 turns. Creatures with 6 or more Hit Dice/Levels are immune to this effect.
Like all undead, Liches are immune to sleep, charm, and hold spells and poison.
Pylactery: This is a hand-held item (brooch, amulet, sword) that safeguards the Lich’s spirit. Unless the item is destroyed, the lich reappears fully healed in 24 hours.
I think the special ability (*) rating should definitely be at least 5. Personally, I would also make the resurrection take significantly longer (I think it is 1d10 days in D&D 3.5 and since when has magic or recovery in ACKS been faster than 3.5; bone-boy can wait a bit). This does allow a bit of time for the players to root around for treasure and phylacteries or to run away with their loot and rest for a bit.
Generally his abilities seem a bit tame compared to either the 3.5 lich or comparable undead ACKS beasties. Invulnerability is a must, as is an energy immunity or two (look at the mummy and vampire to compare). The paralyzing touch seems pretty tame compared to the permanent death-mimicking paralysis of 3.5, the horrors of mummy’s rot, and the vampire’s energy drain, but it is passable. While it is true that a lich’s true power comes from his spells and his true defense is the resurrecting power of his phylactery, there is no need to skimp on his fallback options.
Most importantly, the proper encounter is ONE lich, and then optional minions. Multiple liches working together is a rare exception, and even then, they probably have separate lairs to fit their egos.
One small extra thing that might be a nice addition in ACKS is a way for solitary arcane lich to produce unholy water (or other way to make basic undead permanent) without needing to rely on a cleric for his needs, but that is just an extra add-on.