Pyrewarden has no named monsters. An enemy is a school, which sets its stats and which towers counter it, plus zero or more traits, which the wave number unlocks. Both are below.
Stat multipliers are against the wave's own baseline, so a Geomancy enemy on wave 40 is 1.3× the health of a wave-40 enemy, not of a wave-1 one.
Pyromancy enemies0.9× health · 1.1× speed.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Pyromancy enemy has 0.9× health, 1.1× speed.
Towers of a school that beats Pyromancy hit it for 1.3× damage; towers it beats hit for 0.7×. Pyromancy enemies are beaten by Cryomancy, Geomancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Cryomancy enemies1.1× health · 0.85× speed.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Cryomancy enemy has 1.1× health, 0.85× speed.
Towers of a school that beats Cryomancy hit it for 1.3× damage; towers it beats hit for 0.7×. Cryomancy enemies are beaten by Voltomancy, Chronomancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Voltomancy enemies0.8× health · 1.25× speed.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Voltomancy enemy has 0.8× health, 1.25× speed.
Towers of a school that beats Voltomancy hit it for 1.3× damage; towers it beats hit for 0.7×. Voltomancy enemies are beaten by Cryomancy, Geomancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Toxicology enemies1× health · 1× speed · 15% magic resistance.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Toxicology enemy has 1× health, 1× speed, 15% magic resistance.
Towers of a school that beats Toxicology hit it for 1.3× damage; towers it beats hit for 0.7×. Toxicology enemies are beaten by Arcanum.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Geomancy enemies1.3× health · 0.8× speed · +3 armour.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Geomancy enemy has 1.3× health, 0.8× speed, +3 armour.
Towers of a school that beats Geomancy hit it for 1.3× damage; towers it beats hit for 0.7×. Geomancy enemies are beaten by Aeromancy, Beastmastery.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Umbramancy enemies0.85× health · 1.05× speed · 10% magic resistance.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Umbramancy enemy has 0.85× health, 1.05× speed, 10% magic resistance.
Towers of a school that beats Umbramancy hit it for 1.3× damage; towers it beats hit for 0.7×. Umbramancy enemies are beaten by Radiance, Arcanum, Chronomancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Radiance enemies1.05× health · 1× speed · 20% magic resistance.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Radiance enemy has 1.05× health, 1× speed, 20% magic resistance.
Towers of a school that beats Radiance hit it for 1.3× damage; towers it beats hit for 0.7×. Radiance enemies are beaten by Toxicology, Umbramancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Arcanum enemies0.95× health · 1× speed · 25% magic resistance.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Arcanum enemy has 0.95× health, 1× speed, 25% magic resistance.
Towers of a school that beats Arcanum hit it for 1.3× damage; towers it beats hit for 0.7×. Arcanum enemies are beaten by Umbramancy, Druidism, Beastmastery.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Aeromancy enemies0.85× health · 1.2× speed.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Aeromancy enemy has 0.85× health, 1.2× speed.
Towers of a school that beats Aeromancy hit it for 1.3× damage; towers it beats hit for 0.7×. Aeromancy enemies are beaten by Voltomancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Druidism enemies1.15× health · 0.9× speed.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Druidism enemy has 1.15× health, 0.9× speed.
Towers of a school that beats Druidism hit it for 1.3× damage; towers it beats hit for 0.7×. Druidism enemies are beaten by Pyromancy, Toxicology.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Chronomancy enemies1× health · 0.95× speed · 10% magic resistance.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Chronomancy enemy has 1× health, 0.95× speed, 10% magic resistance.
Towers of a school that beats Chronomancy hit it for 1.3× damage; towers it beats hit for 0.7×. Chronomancy enemies are beaten by Radiance, Druidism.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

Beastmastery enemies1.2× health · 1.05× speed · +2 armour.
Every enemy carries one of the twelve schools, and the school shifts its stats off the wave baseline. A Beastmastery enemy has 1.2× health, 1.05× speed, +2 armour.
Towers of a school that beats Beastmastery hit it for 1.3× damage; towers it beats hit for 0.7×. Beastmastery enemies are beaten by Pyromancy, Aeromancy.
Which schools a map sends is weighted per map — see Maps. On a milestone wave (every 10 waves) the weighting is dropped and all twelve are equally likely.

ArmoredEnemy trait, first seen at wave 10.
Adds 10 flat armour, which is subtracted from every physical hit before it lands.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
FastEnemy trait, first seen at wave 15.
Moves at 1.5× speed but carries only 0.7× the health — it reaches the goal sooner and dies sooner.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
StealthEnemy trait, first seen at wave 20.
No tower can target it at all. Only a Radiance tower sees through stealth; the first Radiance hit strips it permanently, for every tower.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
RegenerationEnemy trait, first seen at wave 25.
Heals 2% of its maximum health every second. Anti-heal effects and stuns both stop it.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
HealerEnemy trait, first seen at wave 30.
Heals every other enemy within 2 tiles for 1% of their maximum health per second. Anti-heal and stuns stop it.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
Magic ShieldEnemy trait, first seen at wave 35.
Absorbs the first 3 hits it takes, whatever their size — three cheap shots strip it as well as three big ones.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.
Spawn on DeathEnemy trait, first seen at wave 40.
Splits into 2 children on death, each at 30% of its maximum health, 1.2× its speed, half its armour and resistance, and half its gold.
Traits enter the pool by wave: armoured at 10, fast at 15, stealth at 20, regeneration at 25, healer at 30, magic shield at 35 and spawn-on-death at 40. Below wave 20 an enemy has at most one trait and a 30% chance of any; 20–29 the chance is 50%; 30–39 up to two traits at 70%; 40–49 up to two at 90%; from wave 50 every enemy gets one to three.