Are creatures that are immune to disease affected by the harm spell?

The harm spell, flavourfully, states it creates a virulent disease

You unleash a virulent disease on a creature that you can see within range.

It later calls out that

Any effect that removes a disease allows a creature’s hit point maximum to return to normal before that time passes.

But no where does it state that being immune to disease (via the Paladin’s Divine Health class feature or otherwise) prevents either the initial damage or the reduction in maximum hit points.

This is in contrast to spells that spell out if immunity works, e.g. sleep.

Does immunity to disease protect you from the harm spell?

Is a creature’s Innate Spellcasting save DC affected by changing ability scores or adding Spellcasting features from another creature?

I’m creating a Svirfneblin Evil Mage by combining the stat blocks for each Evil Mage and Svirfneblin.

A Svirfneblin’s Innate Spellcasting Save DC is 11 and its INT is +1. An Evil Mage’s Spellcasting Save DC is 13 and its INT is +3.

I’m taking the abilities from Evil Mage and Svirfneblin and taking the higher ability scores (and modifiers), does the increased INT modifier from the Evil Mage’s score affect the Innate Spellcasting spell save DC?

Does the number of creatures affected by Sculpt Spells increase with upcasting the spell?

As a level 2 Evocation Wizard, the School allows you to sculpt spells around allies, up to 1 + the spell’s level, allowing them to avoid the effects of the spell. Certain spells, such as Thunderwave, allow you to cast them using a higher level spell slot.

My question is: which level do you use when calculating the amount of allies that can dodge your spell? The actual spell level (for Thunderwave, this is 2), or the level of the spell slot you use when casting (which effectively raises the level of the spell)?

What happens to a spell cast by a target affected by the delayed effect of the Slow spell when he saves?

Part of the description of the Slow spell says:

If the creature attempts to cast a spell with a casting time of 1 action, roll a d20. On an 11 or higher, the spell doesn’t take effect until the creature’s next turn, and the creature must use its action on that turn to complete the spell. If it can’t, the spell is wasted.

The affected spellcaster casts a spell and is hindered by the Slow spell so that his spell does not go off until his next turn, but he saves against the Slow spell at the end of his turn.

As I descend vertically when affected by Feather Fall, can I also move horizontally?

The feather fall spell (PHB, p. 239) says:

Choose up to five falling creatures within range. A falling creature’s rate of descent slows to 60 feet per round until the spell ends. If the creature lands before the spell ends, it takes no falling damage and can land on its feel, and the spell ends for that creature.

Am I able to move horizontally as I descend (to "glide", basically), or can I only fall vertically in a straight line, directly down to the point below me when the spell was cast? Or is this simply something that isn’t specified and is something that the DM is expected to resolve?

This came up in a game I ran a couple of weeks ago. Luckily, this was asked preemptively as they were planning how to storm an orc camp, and the plan was changed before I was pressed for an answer, so I was able to dodge making a ruling entirely. However, if it were to come up again, it is simply up to me (the DM), or is there anything that suggests one or the other ruling?

Does a target affected by compulsion have to dash?

Compulsion states:

Creatures of your choice that you can see within range and that can hear you must make a Wisdom saving throw. A target automatically succeeds on this saving throw if it can’t be charmed. On a failed save, a target is affected by this spell. Until the spell ends, you can use a bonus action on each of your turns to designate a direction that is horizontal to you.

Each affected target must use as much of its movement as possible to move in that direction on its next turn. It can take its action before it moves. After moving in this way, it can make another Wisdom saving throw to try to end the effect.

A target isn’t compelled to move into an obviously deadly hazard, such as a fire or pit, but it will provoke opportunity attacks to move in the designated direction.

Reading the spell again it says they can use their action before moving but what if they don’t? Do they then have to dash to use "as much of [their] movement as possible"?

What about rogues? If they are affected by it (say by either a party member looking for a funny prank, or by an enemy that can cast that spell) do they have to use their cunning action to dash? The spell only permits their action, not their bonus action.

Does a character know the effects of a spell when they are affected by it?

I have created a custom enemy, a golem desgined to investigate new forms of magic, and my players are about to face him.

Among several other stuff, this creature has two spells called high and low arithmetics. Upon failing a saving throw, this spell deals damage each turn to whoever ends their turn on a place lower or higher than the golem, respectively.

My question is, would a character, upon taking damage the first time, know what the conditions for taking the damage would be?

I’ve seen tweet but as far as I’m concerned, that only tells them that indeed, they are victim of a spell. Is there any way for a character to figuring out the rules of a spell? (not counting deducing them by trial and error, of course). I don’t think an arcana check (as is the common rule) would be suitable in this situation since this is a spell that none of them could have ever seen/heard of since it was made by this creature.

What would happen if you cast true polymorph in a creature affected by the Enlarge/Reduce spell? [duplicate]

Partially inspired by this answer, what size of an object could you create with True Polymorph if the target was affected by Enlarge/Reduce? And what size would the object be after Enlarge/Reduce wears off?

True Polymorph says (among other things) (emphasis mine):

Creature into Object. If you turn a creature into an object, it transforms along with whatever it is wearing and carrying into that form, as long as the object’s size is no larger than the creature’s size. The creature’s statistics become those of the object, and the creature has no memory of time spent in this form, after the spell ends and it returns to its normal form.

Enlarge/Reduce says:

Enlarge. The target’s size doubles in all dimensions, and its weight is multiplied by eight. This growth increases its size by one category– from Medium to Large, for example. […]

Reduce. The target’s size is halved in all dimensions, and its weight is reduced to one-eighth of normal. This reduction decreases its size by one category–from Medium to Small, for example. […]

The two spells both require concentration so they would of course have to be cast by two different people. The options I see here are

  1. Medium creature is enlarged to a Large creature and then polymorphed into a Large object. Spell wears off and the Large object is now Medium object since it’s still a valid target for E/R.

  2. Medium creature is enlarged to a Large creature and then polymorphed into a Large object. Spell wears off and the Large object is still a Large object as it’s no longer the original target of the spell since it targeted a creature in this instance.

  3. Medium creature is enlarged to a Large creature and then polymorphed into a Medium object since the creature is normally Medium. E/R ends.

  4. Some option I haven’t thought of.

Is Mirthful Leaps affected by jump multipliers?

In Mythic Odyssey of Theros, the Satyr gain the ability Mirthful Leaps:

Whenever you make a long or high jump, you can roll a d8 and add the number rolled to the number of feet you cover, even when making a standing jump. This extra distance costs movement as normal.

If you have a multiplier on jump distance, such as that provided by the Boots of Striding and Springing…

In addition, you can jump three times the normal distance, though you can’t jump farther than your remaining movement would allow.

… would the +1d8 feet be multiplied by three as well?