Enlarge/Reduce does not affect the stone golem.
Enlarge/Reduce (PHB 237) is a transmutation spell that changes (alters) the properties of a target creature, the target creature Stone Golem (MM 167, MM 170) is immune to that effect.
Immutable Form (MM 170) prevents the alteration
Immutable Form. The golem is immune to any spell or effect that would alter ...
They are still moved
In this spell, it says that the effect of a failed constitution save is both damage and being moved. As you are immune to the damage, the damage acts as if it dealt 0 damage. As the ability never specified that immunity to poison prevent this movement, it would still happen as normal.
You have a few good options against resistance, but immunity is harder to overcome
Against resistance, you have a few spells that can be used to give vulnerability to poison to creature. They are:
hallow (Energy Vulnerability)
contagion (Flesh Rot)
At the DM's fiat, you may also use bestow curse to negate a creature's resistance to poison damage.
Damage Reduction is a specific thing with its own specific rules. It never (unless you are playing with the change in Complete Psionic as opposed to the PHB) applies to damage from spells (even non-energy damage) nor energy damage (even from non-spells), for example, whereas Immunity and Resistance apply even to magical threats. So, while e.g. Energy ...
Adding vulnerability doesn't remove immunity
There's nothing in the rules about any of vulnerability, resistance, or immunity being mutually exclusive. In fact, in the case of vulnerability and resistance, the rules explicitly cover the case of a creature having both (emphasis added):
Resistance and then vulnerability are applied after all other ...
No, it doesn't
The definition of 'vulnerability':
If a creature or object has vulnerability to a damage type, damage of
that type is doubled against it.
If a creature is immune to a damage type, then damage of that type is reduced to 0. This is from a plain English reading of the meaning of "immunity" - to be unaffected by something.
There is nothing ...
The Specific Effect of the Feature Beats the General Immunity
This is a case of specific beats general via a class feature effect.
For instance, an adventurer can’t normally pass through walls, but some spells make that possible.
In this instance, a creature can't normally be damaged by fire, but the class feature makes that possible for a very ...
No, but you could ask your DM for a homebrew
The Elemental Adept feat (Player's Handbook, p. 166) allows a character to ignore resistance to a chosen elemental damage type (acid, cold, fire, lightning, or thunder). Unfortunately, necrotic damage is not one of the damage type options.
You could ask your DM to allow a homebrew version based on the feat:
There is no direct way
For some damage types, there is a way to overcome resistances. Specifically, the Elemental Adept feat does this for exactly one of acid, cold, fire, lightning, or thunder damage. It's conceivable that there someday be an equivalent for necrotic damage, but it does not exist at the moment.
This situation is a result of monster ...
There is strong support for house-ruling that "spectral" implies "magical", based on how the word "spectral" is used in 5e
The accepted answer to this question about Spiritual Weapon states that there is "a decent argument for 'spectral' being equivalent to 'magical force'. However, that determination is up to each table."
Along those lines, the ...
Now here is the funny thing, from the description of Reaping Scythe, it is NOT an attack. Nowhere in the description does it say that an attack is made, it is simply an ability that allows that Avatar of Death to deal damage to creatures within 5 feet of it. No attack roll is made, there is no chance for this to crit, it just happens.
So going by RAW, a ...
Most: Poisoned (434). Least: Incapacitated (1); Unconscious (26).
As of the writing of this answer, there are 1652 total monster/NPC statblocks listed on D&D Beyond.
We can use the filtering options in D&D Beyond's monster listing to see how many monsters/NPCs across all sources are immune to each condition:
This spreadsheet lists the number of monsters from the Monster Manual, Volo's Guide to Monsters, and Mordenkainen's Tome of Foes that are immune to each condition.
According to the spreadsheet:
The most creatures have immunity to the Poisoned condition
The fewest creatures have immunity to the Unconscious condition
And (based on my D&D beyond search) 1 ...