In Mordenkainen's Tome of Foes one can gain Demonic Boons for joining specific cults, changing one's abilities, spells, resistances and even modify combat abilities. Various Demon-Lords (Juiblex, Yeenoghu and Zuggtmoy specifically) also offer an 'equal penalty' for intelligence, wisdom & charisma (though Yeenoghu leaves 'wisdom' untouched) - and this penalty can be quite severe. Given a loss of four to eight points many otherwise-enthusiastic cultists are left quite mindless, which is the point of the cult, story-wise. But what is the minimum? Inquiring minds want to know:
Cultists: Just how stupid can they get?
Low-Ability History: Player Characters in 5e may have a minimum of three and maximum of twenty for any ability score. Note that previous editions even had negative ability scores, especially charisma (this gave fear-aura abilities) - but such a mechanic is not in 5e. Many automatons, oozes and slimes in the first edition of AD&D had 'non-intelligent' or a zero-intelligence score - but with 5e even iron golems have a surprisingly clever score of 3. Even 'utterly mindless' (i.e. 'actually devoid of all brain-matter') undead non-player skeletons only have a penalty of -4 (DM's Guide p.282).
So, just to specify &/or reiterate: Do cultist-creatures (humanoid or otherwise) have a minimum intelligence score, if any?
Reason for asking: Many spells focus easily on targets with low ability scores, especially those with low wisdom - this would change game-play. Also, if any creature's lowest score was below that of a Violet fungus, the target may enter a non-ambulatory &/or vegetative state. If this reduction were allowed to go below zero, one must assume instant death for any such gormless person joining such cults (this is a very possible and reasonable ruling - demonic cults are not known for their kindness nor protection of specific minorities). Thus, any rulings - even Crawfordonian ones - would be welcome.