[RPG] Is the homebrew lower-powered Lich’s CR calculated correctly


I created a "Lesser Lich" so my party would be able to fight something interesting in the story I have. In my game, a lich undergoes development changes the first time it "ascends(descends) to lichdom." It first becomes a protolich (lowest level) for 1d10 days. This creature is mostly feral, acting more instinctively. It also gains no lich lair bonus. It then becomes a "Lesser Lich" for another 1d20 days or until it makes an appropriate number of sacrifices to its phylactery. This made up stuff doesn't apply to a lich that was already a full lich.

Here is the stat block I came up with:

enter image description here

My question is, is my "Lesser Lich" really a CR 10 (12 in lair)? I used the DMG to calculate, but it was a bit confusing.

My Calculations

Defensive CR 4 (hp 2, AC 10; move 2 up 2, 4)

Offensive CR 16 (this I really guessed on… dmg/round? 50-100?)

average the two: 10

My damage per round, I had to guess. If the lich casts, "disintegrate" it can do a max damage of 100. That's is one big move. If it doesn't… I have no idea how much damage it does in a round.

Sources / Credits

addition / edit:

Based on the feedback, I lowered the level of my "lesser lich" to an 8th level caster. This cuts 5th and 6th level spells and lowers the HP to ~74. I also lowered the AC to 15, reduced legendary actions to 2 / turn, and recalculated damage. Based of this, the average damage I got was ~ 57/ round (Blight hitting 2 creatures for average damage, and 2 ray of frosts). All this gives me a def CR of 8(?) and Off Cr of 10(?). CR is 9 out of lair and 12 in lair(?):

lesser lich 2

Based on my own play test vs a group of 4, the second block is probably a CR 6-7.

Best Answer

CR10 is low for this creature. Here's how I computed it:

Assuming a target CR of 10, offensively you have:

  • 111+ damage/round (3x Ray of Frost plus Cloudkill or Disintegrate)
  • +9 attack bonus
  • DC17 save

Damage is CR18, but attack and save are low for that and drop it to CR17.

On defense you have:

  • 86 HP
  • +20 effective HP for legendary resistance 1/day
  • x 1.25 for significant resistances
  • AC 17
  • Three saving throw bonuses (effective AC +2)
  • Access to globe of invulnerability and counterspell

Adjusted HP is CR5, AC is 4 points higher than suggested for that CR to increase defensive DC to 7. The defensive spells are worth (I think) at least two CRs if not more. Bear in mind that with an Intelligence of 20 the lich will probably be prepared for an encounter with the globe and mirror image up. This means it ignores spells (including counterspell) of level 5 or lower, and it can use its own counterspell to shut down one dispel magic attempt per turn.

So conservatively it's offensive CR17 and defensive CR9 or more, which average to CR13 without the lair bonuses. CR10 seems like a significant underestimate.

The lore around the creature is fine, however.