An experiment with mechanics. Looks really powerful, a final villain of some sort. I can't imagine anything less of a warband going against this thing.
It uses glog magic mechanics. If you don't know what that is, basically roll 1-3 d6. When the effects mention [dice], it means the number of dice spent. When they mention [sum] it means the total of the values rolled. Check out the mechanics here. This lich works a little differently though, see below.
Lich 3 hp, 6 STR, 6 DEX, 16 WIL
A lich has 16 WIL, one spell slot, and one magic die per point of WIL. They can only use the highest slot available. To use the spells, they have to spend WIL points to gain the magic dice necessary (max 3). A lich's magic dice never return to the pool until they perform a ritual. They don't suffer dooms or mishaps. At WIL 0 they don't go mad but they're exhausted and unable to act.
Example: The lich is left with 14 WIL. They can either use Fireball or hold the slot to use Counterspell. They use Fireball and spend 3 magic dice. They lose 3 points of WIL. Next turn they're gonna have one of the spells in the 11th slot available: Animate Dead or Counterspell
1. Dimension Door (costs 1 WIL) or Ray of Frost
2. Disintegrate or Globe of Invulnerability
3. Animate Dead or Counterspell
4. Animate Dead or Counterspell
5. Dimension Door (costs 1 WIL) or Ray of Frost
6. Fireball or Counterspell
7. Fireball or Counterspell
8. Disintegrate or Globe of Invulnerability
9. Dimension Door (costs 1 WIL) or Ray of Frost
10. Mirror Image or Acid Arrow
11. Animate Dead or Counterspell
12. Mirror Image or Acid Arrow
13. Disintegrate or Globe of Invulnerability
14. Fireball or Counterspell
15. Mirror Image or Acid Arrow
16. Mirror Image or Acid Arrow
Acid Arrow: Hits [dice] random body or hand slots, DEX save to avoid. If there's an object in the slot, it's destroyed. If the slot is empty, it's filled with acid that causes d6 STR damage per slot this round and at the end of every subsequent round until washed (only count the highest die if rolling multiple)
Animate Dead: Raise [dice] dead bodies under your control. Armor as worn, d6 hp, 6 DEX, 0 WIL, damage as weapon
Counterspell: Reaction. Negate the effect of a spell if the caster's WIL is lower than [sum]. You may also choose to reflect it back on the caster
Dimension Door (costs 1 WIL): Materializes a portal out of thin air that teleports you to a tethered location. An opponent has to DEX save to act before it closes.
Disintegrate: A ray that hits for [sum] damage. A creature that receives STR damage from this spell disintegrates instantly.
Fireball: [sum] damage blast
Globe of Invulnerability: A globe shields you from any attack or spell for [dice] rounds.
Mirror Image: Create [dice] illusory copies of yourself. If they're attacked, they're instantly destroyed
Ray of Frost: d8 damage. If STR damage is taken the opponent is slowed for [dice] round. Slowed characters can only take one action per round (either move OR attack, or any other action) and always fail DEX saves.
Let me know your thoughts.