Level
5th
Casting Time
1 Action
Range/Area
90 ft.
Components
V, S, M *
Duration
Concentration
1 Minute
School
Enchantment
Attack/Save
WIS Save
Damage/Effect
Paralyzed
Choose a creature that you can see within range. The target must succeed on a Wisdom saving throw or be paralyzed for the duration. This spell has no effect on undead. At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the spell ends on the target.
At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, you can target one additional creature for each slot level above 5th. The creatures must be within 30 feet of each other when you target them.
* - (a small, straight piece of iron)
Chains of Carceri might be broken…
I'm in the camp of "hold spells aren't affected by mind blank", but I do respect the opposite argument's logic. Here's my counter:
The PHB describes the school of enchantment as "spells [which] affect the minds of others, influencing or controlling their behavior." That seems pretty condemning, but it also says: "The schools of magic help describe spells; they have no rules of their own, although some rules refer to the schools." I argue the hold spells are only classified as enchantments due to their ability to control the target's behavior by way of paralysis, which is a physical condition rather than a charm or something like the command spell. In contrast, mind blank is very geared towards protection against emotional and intellectual manipulation or detection - like the charmed condition or the command spell. It even specifies protection against a school of magic within its text - divination - but says nothing about protection from enchantments.
As for Wisdom saving throws, the DMG suggests that they be used for "resisting effects that charm, frighten, or otherwise assault your willpower." The only relevance for hold spells is an assault on willpower; you could certainly argue that to be an affect on the target's mind, but considering the text of the spells in question I'd call it a stretch.
tl;dr - the only direct correlation between hold spells and mind blank is the former's classification as enchantment spells, which by RAW is a descriptive tag against which mind blank specifically omits any protection.
I don't totally get it either.
It doesn't work on undead but does work on constructs, elementals, and fiends.
Undead are basically dark-magic constructs.
If it only worked on organic creatures or ones with actual minds, it wouldn't work on constructs.
I can understand it not working on ghost/spirit types, since their body is not physical at all.
But if it works on living flame essence and demons made out of evil-stuff it oughta work on skellies and zombos too.
Banishment is just a very good spell. Also, if a creature is not native to your plane and as long as you keep concentration for the duration (a minute) the creature is unable to return, completely “banishing” it.