Monstrosity

Small Monstrosity

 * Cockatrice – Unaligned – MM 42
 * Darkmantle – Unaligned – MM 46

Medium Monstrosity

 * Basilisk - Unaligned - MM 24
 * Doppelganger – N – MM 82 (Shapechanger)
 * Ettercap – NE – MM 131
 * Grick – N – MM 173
 * Harpy – CE – MM 181
 * Medusa – LE – MM 214
 * Mimic – N – MM 220 (Shapechanger)
 * Peryton – CE – MM 251
 * Piercer – Unaligned – MM 252
 * Rust Monster – Unaligned – MM 262
 * Yuan-ti Malison – NE – MM 309 (shapechanger)
 * Death Dog – NE – MM 321

Large Monstrosity

 * Ankheg - Unaligned - MM 21
 * Bulette - Unaligned - MM 34
 * Carrion Crawler - Unaligned - MM 37
 * Centaur - Neutral Good - MM 38
 * Chimera - Chaotic Evil - MM 39
 * Displacer Beast – LE – MM 81
 * Drider – CE – MM 120
 * Gorgon – Unaligned – MM 171
 * Grick Alpha – N -  MM 173
 * Griffon – Unaligned – MM 174
 * Hippogriff – Unaligned – MM 184
 * Hook Horror – N – MM 189
 * Lamia – CE – MM 201
 * Manticore – LE – MM 213
 * Merrow – CE – MM 219
 * Minotaur – CE – MM 223
 * Guardian Naga – LG – MM 234
 * Spirit Naga – CE – MM 234
 * Owlbear – Unaligned – MM 249
 * Phase Spider – Unaligned - 334
 * Young Remorhaz – Unaligned – MM 258
 * Roper – NE – MM 261
 * Androsphinx – LN – MM 281
 * Gynosphinx – LN – MM 282
 * Umber Hulk – CE – MM 292
 * Yeti – CE – MM 305
 * Yuan-ti Abomination – NE – MM 308 (Shapechanger)

Huge Monstrosity

 * Behir - Neutral Evil - MM 25
 * Hydra – Unaligned – MM 190
 * Remorhaz – Unaligned – MM 258
 * Abominable Yeti – CE – MM 306

Gargantuan Monstrosity

 * Kraken – CE – MM 197 (titan)
 * Purple Worm – Unaligned – MM 255
 * Roc – Unaligned – MM 260

Titan Monstrosity

 * Tarrasque