Boss monsters are a hallmark of adventure design. In the climactic battle, the PCs end the boss’s schemes and save the day.
Especially at lower levels though, boss monsters can be dull. They are frequently guileless and lack interesting abilities beyond swinging a sword and commanding underlings to an early grave.
So how do we fix boss monsters? We rebuild them into dynamic stat blocks.
See previous Boss Fights articles here!
The Sausage Making
Building a dynamic boss battle involves several steps. To make your own, follow these steps:
1. Separate the monster’s attitude toward combat into three phases.
2. Break out the monster’s published stat block to match each phase.
3. Use or modify existing abilities that match the attitude for each phase. To improve boss effectiveness and survivability, add new reactions and bonus actions to make good use of the action economy.
4. Introduce lackeys with low hit points. Several full-blown allies can bog down combat, but lackeys (with a fraction of hit points that a standard monster of their type would have) provide an obstacle without slowing the tempo.
5. Add lair actions. A clever boss fights on their own terms. Even cornered, a boss monster chooses the battlefield, which grants them special actions on their turf.
Each article focuses on different aspects of these boss fights. This article focuses on modifying existing abilities that match the tone of the battle for each phase.
Gynosphinx
This article adapts the gynosphinx from the core rules. Her lair is the sandy antechamber to a forgotten pyramid brimming with powerful artifacts. The sphinx relies on lackeys to protect her lair: anubians and possessed pillars (see Tome of Beasts) and wind eaters (see Creature Codex).
The gynosphinx doesn’t solely depend upon lackeys, however. When interacting with enemies, she speaks riddles that interact with the runes in her lair. Until they are solved, these riddles target foes, transform terrain, and empower lackeys.
| Solving These Riddles In this fight, the gynosphinx weaponizes her riddles. While the phrasing and formulation of riddles is beyond this article, the game mechanics for solving them isn’t! Once the gynosphinx issues her riddle, the lair action takes effect. Once the riddle is solved, the effect is muted until the next lair action begins. Any player can try to answer a riddle by using their reaction. This limits the number of times a character can reasonably guess in a 6 second round. Sometimes riddles are more difficult than expected. PCs who use their reaction and make a DC 15 Wisdom (Insight) check garner a clue. The PC can subsequently guess as part of their reaction after waiting at least 5 initiative counts. Sometimes players aren’t good at riddles, even if their characters should be. A PC using their reaction and making successful DC 21 Wisdom (Insight) check knows the answer outright. |
Each phase represents the gynosphinx’s reaction to encroachment upon her lair: gynosphinx proctor, gynosphinx bulwark, and gynosphinx ravager.
While normally CR 11, this gynosphinx is CR 13 while in her lair. PCs who defeat the gynopshinx ravager receive 10,000 XP.
In the initial phase, the gynosphinx toys with her foes, using spells and lair actions to probe their defenses and learn their abilities. The gynosphinx also summons possessed pillars that batter foes within their reach.
Sphinx Proctor (Phase 1)
Large Monstrosity, Usually Lawful Neutral
Armor Class 17 (natural armor)
Hit Points 68 (8d10 + 24)
Speed 40 ft., fly 60 ft.
| STR | DEX | CON | INT | WIS | CHA |
| 18 (+4) | 15 (+2) | 16 (+3) | 18 (+4) | 18 (+4) | 18 (+4) |
Skills Arcana +12, History +12, Perception +8, Religion +8
Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities psychic
Condition Immunities charmed, frightened
Senses truesight 120 ft., passive Perception 18
Languages Common, Sphinx
Challenge 4 (1,100 XP) Proficiency Bonus +4
Inscrutable. The sphinx is immune to any effect that would sense her emotions or read her thoughts, as well as any divination spell that she refuses. Wisdom (Insight) checks made to ascertain the sphinx’s intentions or sincerity have disadvantage.
Legendary Resistance (1/phase). If the sphinx fails a saving throw, she can choose to succeed instead.
Magic Weapons. The sphinx’s weapon attacks are magical.
Spellcasting. The sphinx casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 16):
At will: mage hand, minor illusion, prestidigitation
3/day each: darkness, detect magic, shield
2/day each: dispel magic, remove curse, suggestion
1/day each:banishment, greater invisibility, tongues
Spells per day are shared among the three phases.
ACTIONS
Multiattack. The sphinx makes two claw attacks.
Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.
BONUS ACTIONS
The Temple Lives (1/phase). The sphinx summons 1d4 + 1 lackeys (possessed pillars with 10 hp and without the Steal Weapons feature), which act on initiative count 15.
LAIR ACTIONS
On initiative count 20 (losing initiative ties), the sphinx issues a riddle as part of its lair action to cause one of the following effects:
- Eternal Duty. Lackeys have +2 bonus to their AC and make one additional slam attack as a part of their Multiattack action.
- Flash Frozen. Gusts of frigid air assault the sphinx’s foes. At the start of each enemy creature’s turn, that creature must make a DC 18 Constitution saving throw or take 13 (3d8) cold damage. If a creature fails by 5 or more, that creature is also incapacitated until the riddle is solved or the next lair action (whichever comes first).
- Uplift. Three cyclones erupt, each in a 10-foot radius. Each creature in the cyclone must make a DC 18 Strength saving throw or rise vertically 20 feet and remain suspended for the duration of the riddle. If a creature fails by 5 or more, that creature takes 7 (2d6) bludgeoning damage after falling when the riddle effect ends.
In this phase, the gynosphinx calls upon the defense properties of the sand in her lair. She also magically shifts lackeys around her lair to prevent harm from befalling its allies. The gynosphinx now summons wind eaters, who target spellcasters and other foes that rely on verbal instructions.
Sphinx Bulwark (Phase 2)
Large Monstrosity, Usually Lawful Neutral
Armor Class 17 (natural armor)
Hit Points 68 (8d10 + 24)
Speed 40 ft., fly 60 ft.
| STR | DEX | CON | INT | WIS | CHA |
| 18 (+4) | 15 (+2) | 16 (+3) | 18 (+4) | 18 (+4) | 18 (+4) |
Skills Arcana +12, History +12, Perception +8, Religion +8
Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities psychic
Condition Immunities charmed, frightened
Senses truesight 120 ft., passive Perception 18
Languages Common, Sphinx
Challenge 4 (1,100 XP) Proficiency Bonus +4
Inscrutable. The sphinx is immune to any effect that would sense her emotions or read her thoughts, as well as any divination spell that she refuses. Wisdom (Insight) checks made to ascertain the sphinx’s intentions or sincerity have disadvantage.
Legendary Resistance (1/phase). If the sphinx fails a saving throw, she can choose to succeed instead.
Magic Weapons. The sphinx’s weapon attacks are magical.
Spellcasting. The sphinx casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 16):
At will: mage hand, minor illusion, prestidigitation
3/day each: darkness, detect magic, shield
2/day each: dispel magic, remove curse, suggestion
1/day each: banishment, greater invisibility, tongues
Spells per day are shared among the three phases.
ACTIONS
Multiattack. The sphinx makes two claw attacks.
Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.
BONUS ACTIONS
Shhh! (1/phase). The sphinx summons 1d4 + 1 lackeys (wind eaters with 10 HP and without the Innate Spellcasting feature), which act on initiative count 10.
LAIR ACTIONS
On initiative count 20 (losing initiative ties), the sphinx issues a riddle as part of her lair action to cause one of the following effects:
- Hasty Circulation. When targeted by a weapon or spell attack, lackeys can teleport up to 60 ft. to an unoccupied space they can see. The teleport occurs after the attack is declared but before the attack is resolved.
- Quicksand. Sifting sands grasp at the sphinx’s foes. At the start of each enemy creature’s turn, that creature must make a DC 18 Dexterity saving throw or take 13 (3d8) force damage. If a creature fails by 5 or more, that creature is also grappled until the riddle is solved or the next lair action (whichever comes first).
- Sudden Sinkhole. Whirling winds carve 3 pits into the lair, each 10 ft. squares. Creatures who walk into the pits must make DC 18 Dexterity saving throws or have their walking speed reduced by 10 feet. PCs who fail by 5 or more lose all remaining walking speed.
In the final phase, the gynosphinx acknowledges that the battle isn’t going her way. She uses spells to confuse her foes, and it employs her bonus actions to flood the battlefield with anubian allies. If unsuccessful, the gynosphinx looks to escape. After all, the foes may likely return from whence they entered, and the gynosphinx will have a second bite at the apple.
Sphinx Ravager (Phase 3)
Large Monstrosity, Usually Lawful Neutral
Armor Class 17 (natural armor)
Hit Points 68 (8d10 + 24)
Speed 40 ft., fly 60 ft.
| STR | DEX | CON | INT | WIS | CHA |
| 18 (+4) | 15 (+2) | 16 (+3) | 18 (+4) | 18 (+4) | 18 (+4) |
Skills Arcana +12, History +12, Perception +8, Religion +8
Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities psychic
Condition Immunities charmed, frightened
Senses truesight 120 ft., passive Perception 18
Languages Common, Sphinx
Challenge 5 (1,800 XP) Proficiency Bonus +4
Inscrutable. The sphinx is immune to any effect that would sense her emotions or read her thoughts, as well as any divination spell that she refuses. Wisdom (Insight) checks made to ascertain the sphinx’s intentions or sincerity have disadvantage.
Legendary Resistance (1/phase). If the sphinx fails a saving throw, she can choose to succeed instead.
Magic Weapons. The sphinx’s weapon attacks are magical.
Spellcasting. The sphinx casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 16):
At will: mage hand, minor illusion, prestidigitation
3/day each: darkness, detect magic, shield
2/day each: dispel magic, remove curse, suggestion
1/day each: banishment, greater invisibility, tongues
Spells per day are shared among the three phases.
ACTIONS
Multiattack. The sphinx makes two claw attacks.
Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.
BONUS ACTIONS
Death in the Sands (2/phase). The sphinx summons 1d4 + 1 lackeys (anubians with 10 HP), which act on initiative count 5.
LAIR ACTIONS
On initiative count 20 (losing initiative ties), the sphinx issues a riddle as part of her lair action to cause one of the following effects:
- Guiding Strike. When a lackey hits an enemy creature with a melee attack, the next attack roll against that creature has advantage. This lasts until the riddle is solved or the next lair action (whichever comes first).
- Hallucination. The sphinx’s riddles confuse her foes with hallucinatory terrain. Before moving, enemy creatures must make DC 18 Intelligence saving throws or move at half speed. Creatures who fail by 5 or more move at full speed but in a random direction.
- Mind Games. The sphinx’s cunning riddles torment the minds of her enemies. At the start of each enemy creature’s turn, that creature must make a DC 18 Wisdom saving throw or take 13 (3d8) psychic damage. If a creature fails by 5 or more, that creature is also stunned until the riddle is solved or the next lair action (whichever comes first).
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About Benjamin Eastman
Benjamin L. Eastman was introduced to D&D by his four closest friends—who immediately betrayed his trust by sacrificing his first character to a demonic artifact. Undeterred, he’s played all manner of RPGs in the intervening years. In addition to writing Warlock Lairs and monsters for Kobold Press, he’s contributed to the Stargate RPG and Americana, and co-authored DMs Guild adventures including Baby Tarrasque. He is perhaps proudest of the bar brawl—his first published monster in the Creature Codex.
