Darkanas - homemade boss

[kenner]

Hello, I am semi new to DnD. 5e is my first edition and I am taking on the wonderful job of home brewing a campaign. With such a task I am creating a lot of my own content. Today's issue though is I have created a boss and I was hoping to get some feedback to see what i did good and what will just be awful. This fight is created for 5 level 10 characters. Without further wait below is Darkanas, an evil warlock hellbent on becoming a lich.

Darkanas
Medium humanoid half-orc, chaotic evil
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Armor Class 13
Hit Points 144
Speed 30 ft
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STR DEX CON INT WIS CHA
8(-1) 8(-1) 15(+2) 17(+3) 15(+2) 17(+3)
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Saving Throws lnt +6, Wis +6
Skills Arcana +6, History +6
Senses passive Perception 14
Languages Common and Orc
Challenge

Spellcasting. Darkanas is a 9th-level spell caster. Its
spellcasting ability is Charisma (spell save DC 14, +6 to
hit with spell attacks). He has the following warlock
spells prepared :

Cantrips (At Will): Chill Touch, Eldritch Blast, Minor Illusion, poison Spray
1st level (5 Slots): Armor of Agathys, Arms of Hadar, Hex, Witch Bolt
2nd level (4 Slots): Cloud of Daggers, Hold Person, Mirror Image, Misty Step
3rd level (4 Slots): CounterSpell, Fear, Hunger of Hadar, Vampiric Touch
4th level (4 Slots): banishment, Blight, Dimension Door

Action: Cast two spells per turn

Special action
Randomly once per combat round roll 1d12
1-6
do nothing
7-10
Summon Skeletons: summon 1d6 skeletons with spider climb
11-12
Summon Minotaur Skeletons: summon 1d4 minotaur skeletons

[Lalliman]

It's a bit hard to appraise because NPCs, especially bosses, are not usually built in the same way as player characters.

According to the monster creation guidelines on page 274 of the DMG, I would estimate him to be a CR 7, based on offensive CR 10 and defensive CR 4. Offensive CR is based on his ability to cast Blight twice per turn. His damage output will drop drastically after two rounds, but I still think CR 7 is fair because of the sheer versatility of his spells. In theory, a CR 7 creature assisted by a few skeletal minions should be a medium to hard encounter for five 10th level players.

That being said, this character will be extremely swingy. On the one hand, his AC and physical saves are poor, so he will go down quite quickly to focus fire, can be easily stun-locked by a monk, and will be generally unable to maintain a concentration spell.

On the other hand, this character could be very nasty if played intelligently. He can use Mirror Image, Vampiric Touch, and various control effects to keep himself alive as long as possible, summoning new skeletal minions every two rounds. In the right environment he can pull the particularly nasty trick of teleporting 500 feet away with Dimension Door, forcing the players to spend five to ten rounds catching up to him, by which point he'll have spawned two to four new batches of minions. Point is, that minion-spawning ability is pretty exploitable. It might be better to simple have him start the battle with a bunch of undead at his side.

My advice for the future is that if you want to build a proper boss, avoid building it like a player character, especially a caster. PC caster classes tend to be a) fragile and easily defeated when encountered alone, and b) highly dependent on resource expenditure, which when applied to an NPC muddies the water and makes it hard to estimate their power level. Instead, build it like an NPC: give it a solid defence (i.e. make sure its defensive CR is at least close to its offensive CR), give it a narrow selection of essential abilities, and give it Legendary Resistance to avoid being stun-locked or otherwise screwed by save-or-suck spells. If it's meant to be faced on its own (which this one isn't), give it legendary actions.

Admittedly, some people don't like this method of applying different rules to PCs and NPCs, so it's up to you to decide if you're ok with that approach. But it's certainly the most convenient way to ensure that a boss battle doesn't end up one-sided.

[kenner]

EDITS: higher AC and HP, added damage and condition immunities, removed spell slots, Changed skeletons to make it more of a start and add as needed.


Darkanas
Medium humanoid half-orc, chaotic evil
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Armor Class 15
Hit Points 198
Speed 30 ft
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STR DEX CON INT WIS CHA
8(-1) 8(-1) 15(+2) 17(+3) 15(+2) 17(+3)
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Saving Throws lnt +6, Wis +6
Skills Arcana +6, History +6
Damage Immunities psychic; bludgeoning, piercing, and
slashing from non magical weapons
Condition Immunities charmed, paralyzed, petrified, frightened
Senses passive Perception 14
Languages Common and Orc
Challenge

Spellcasting. Darkanas is a 9th-level spell caster. Its
spellcasting ability is Charisma (spell save DC 14, +6 to
hit with spell attacks). He has the following warlock
spells prepared :

Cantrips: Chill Touch, Eldritch Blast, Minor Illusion, poison Spray
1st level: Armor of Agathys, Arms of Hadar, Hex, Witch Bolt
2nd level: Cloud of Daggers, Hold Person, Mirror Image, Misty Step
3rd level: CounterSpell, Fear, Hunger of Hadar, Vampiric Touch
4th level: banishment, Blight, Dimension Door

Action: Cast two spells per turn


Battle starts with 5 skeletons with spider climb
Have Minotaur Skeletons ready if needed