by allstar64
For the record the rules seem to imply that mask monsters are NOT Spawn monstersPage 7 Dunwich Horror rulebook.
Spawn Monsters
Spawn monsters are indicated by a red circle in the
lower left corner of their movement side, next to their
dimensional symbol. Like “Mask” monsters, Spawn
monsters are not added to the monster cup. Instead, they
enter play through special rules. For example, the
Dunwich Horror enters play when the Dunwich Horror
track on the Dunwich board fills up, while the Servants
of Glaaki enter play through Glaaki’s “Undead
Servants” ability.
Additionally, Spawn monsters do not count against the
monster limit and never go to the Outskirts, nor can they
ever be claimed as monster trophies.
Spawn monsters are indicated by a red circle in the
lower left corner of their movement side, next to their
dimensional symbol. Like “Mask” monsters, Spawn
monsters are not added to the monster cup. Instead, they
enter play through special rules. For example, the
Dunwich Horror enters play when the Dunwich Horror
track on the Dunwich board fills up, while the Servants
of Glaaki enter play through Glaaki’s “Undead
Servants” ability.
Additionally, Spawn monsters do not count against the
monster limit and never go to the Outskirts, nor can they
ever be claimed as monster trophies.
I haven't seen anything to imply that monsters are special in anyway with regards to the monster limit.