| Kileanna |
What is the composition of the party?
Is the boss going to have minions?
I strongly suggest that you give him some minions, as the encounter could be too eas otherwise. The action economy is a great advantage, and a single enemy is in a serious risk of being defeated on a single turn.
The other aspects of the encounter seem balanced. You can play with the lich's spells selection to do the encounter more easy or more complicated without riisng or lowering the CR. Only you know what kind of strategies and tricks your players favor, so tailor the encounter so you can counter them to avoid the lich being defeated too quick.