RAW, you cannot become invisible via moving fast
As the other answers have stated, there are no rules that imply this. When a monk reaches 18th level, they gain access to the Empty Body class feature (PHB, p. 79):
Beginning at 18th level, you can use your action to spend 4 ki points to become invisible for 1 minute. During that time, you also ...
You're using the spell incorrectly. Note that the condition that causes the spell to damage a creature is when the creature enters the beam. It takes movement on the part of the creature (including forced movement) to do that. It does not cause damage when the beam just passes over a creature. As you note, that would be super powerful for a 2nd level ...
Cunning Action absolutely does let you Dash again, but Dash doesn't work quite like you're remembering (PHB, p. 192):
When you take the Dash action, you gain extra movement for the current turn. The increase equals your speed, after applying any modifiers.
Speed and movement are separate concepts in 5e. Usually your allowed movement for the turn = your ...
As soon as combat starts, everyone needs to abide by the movement rules
I would suggest telling them that as soon as combat starts, everyone needs to abide by the movement rules, regardless of whether they're engaged with an enemy. Make it clear that the reason you gloss over movement out of combat is because movement is not generally important at that point....
Heavy Armor. Heavier armor interferes with the
wearer’s ability to move quickly, stealthily, and freely.
If the Armor table shows “Str 13” or “Str 15” in the
Strength column for an armor type, the armor reduces
the wearer’s speed by 10 feet unless the wearer has a
Strength score equal to or higher than the listed score.
Since this question was asked, Jeremy Crawford has changed his mind on how this works.
In the April Rules Answers column for Sage Advice, Crawford has this to say:
Does moonbeam [or Spirit Guardians] deal damage when you cast it? What about when its effect moves onto a creature? The answer to both questions is no.
He goes on to elaborate:
Reading the ...
In a tweet from Jeremy Crawford, he says:
When a spell's description uses "enter" in relation to an AoE, the entering has to be voluntary only if the text says so.
By itself, it seems to imply that moving the Moonbeam counts as "entering".
But, in a Sage Advice article, he clarifies this:
Our design intent for such spells is this: a ...
From the Movement and Position section on page 70 of the Player's Basic Rules:
On your turn, you can move a distance up to your
speed. You can use as much or as little of your speed as
you like on your turn, following the rules here.
Your movement can include jumping, climbing, and
swimming. These different modes of movement can
be combined with ...
Short simple answer here. No you can't, you can only mount or dismount once per turn. Player's Handbook, page 198:
Mounting and Dismounting
Once during your move, you can mount a creature that is within 5 feet of you or dismount.
Unless I missed something, this is not how dash works.
Having two actions from Haste means he can Dash twice, so that's 600 feet of movement.
When you take the Dash action, you gain extra Movement for the current turn. The increase equals your speed, after applying any modifiers.
Note that Dash does not increase your speed, it just gives you ...
There are no specific rules for what happens if knocked prone while swimming, therefore, from a purely mechanical standpoint, we must assume that the general rule applies.
From PHB 292...
A prone creature's only movement option is to crawl, unless it stands up and thereby ends the condition. (Note: Crawling costs 2 feet of movement per foot moved. ...
Coming from a D&D point of view...
The game becomes a lot more mobile, speed is more valuable, the concept of front-liner diminishes, and being at range is either difficult or not important.
I tried this for a one-shot once with a couple of new players, and we removed OAs for simplicity's sake. The more experienced players at the table had some fun ...
Yes, you can!
Look at Players Handbook p. 190.
Moving between Attacks
If you take an action that includes more than one weapon attack, you can break up your movement even further by moving between those attacks.
Check out the Player's Handbook, page 192:
Squeezing into a Smaller Space:
A creature can squeeze through a space that is large enough for a creature one size smaller than it. Thus, a Large creature can squeeze through a passage that's only 5 feet wide. While squeezing through a space,
a creature must spend 1 extra foot for every foot it moves there, ...
From the Player's Handbook:
High Jump. When you make a high jump, you leap into the air a number
of feet equal to 3 + your Strength modifier if you move at least 10
feet on foot immediately before the jump. When you make a standing
high jump, you can jump only half that distance. Either way, each foot
you clear on the jump costs a foot of movement. In ...
...when the creature enters the area for the first time on
a turn or starts its turn there...
The orcs are not entering the area, the area is changing to include them. So, your hypothetical cleric rides within 15 feet of 48 orcs, but the damage is only dealt to the last ten or so that are still within 10 feet of him when their turns start.
It's unclear whether bonuses to "your speed" apply to flying speeds. If they don't, the fastest you can go is:
Shapechange into a Storm Giant: 50 ft.
Monk level 15 Unarmored Movement: +25 ft.
Barbarian level 5 Unarmored Movement: +10 ft.
Mobile feat: +10 ft.
Longstrider spell: +10 ft.
Boots of Speed: Double speed
Haste spell: Double speed
Dash action ×...
A level 18 hasted wood elf monk can move at 68 mph.
The speed with haste is correct, but you make some mistakes with the Dash action. Dashing does not double a creature's speed, rather it grants a creature extra movement equal to its speed. Therefore, the hasted wood elf monk can move 600 feet per turn, or 68 mph.
However, that's not even close to ...
Variant Human (30ft) with Mobile Feat (+10ft) with 2 Monk levels (+10ft from Unarmored Movement, and Step of the Wind) + 3 Totem Barbarian levels (+15ft Elk Totem during Rage) + 2 Fighter Levels (Action Surge).
Mr. Bolt has to run 100m in 9.4/s, or 328ft in 9.4s, or 210ft/turn (average speed). His base speed is 50ft.
As a setup, Bolt rages to ...
The condition states everything you're not allowed to do:
Actions (which also prevents Bonus Actions, per PHB p. 189: "anything that deprives you of your ability to take actions also prevents you from taking a bonus action")
Moving is none of those, so you can do it.
Keep in mind, though, that most effects that incapacitate also ...
The character finishes the jump on the next turn.
At the snapshot in time at the end of the character's turn the character is in mid-air. On its next turn, it finishes the jump.
By the Rules
From the Movement and Position section on page 70 of the Player's Basic Rules:
On your turn, you can move a distance up to your speed. You can use as much or as little ...
This question is an example of how a DM should deal the concept of Rules Lawyer vs Playability in the game.
Given the way the rules are written, there's a loophole that can be exploited. Yes, it's possible to string those actions together.
However, logically, take a minute to think about what you ask. In a round (which is 6 seconds), can you: move 120', ...
Players Basic Rules, pg 71
Moving Around Other Creatures
If you leave a hostile creature’s reach during your move,
you provoke an opportunity attack, as explained later in
Players Basic Rules, pg 73
You can make an opportunity attack when a hostile
creature that you can see moves out of your reach.
So yes, you can ...
Yes, and they don't need to ready an action to do it
Say their movement is 30ft. They expend their movement for 30ft, use their action to Dash for an extra 30ft, then Bonus action to Dash again with an additional 30ft.
90ft in total - triple their base movement
Here's a question that covers Dashing twice on the same round:
Can you dash twice on the same ...
The answer to this is on page 196 of the PHB.
Using Different Speeds
If you have more than one speed, such as your walking
speed and a flying speed, you can switch back and forth
between your speeds during your move. Whenever you
switch, subtract the distance you've already moved from
the new speed. The result determines how much farther
you can move. If ...
There is no such speed in D&D 5e. You will have to add it yourself.
There is no speed in D&D 5e that causes spontaneous invisibility.
Since you are deciding that there is such a speed, but D&D can’t tell you what it is, it’s up to you as the DM. You’ll have to pick a speed and create your own house rule that says, “a Speed of [whatever you ...
Swimming is not flying
As far as I am aware, flying is never defined as a game term, which means the word takes its normal English meaning: moving through the air under one's own power. I don't think most people would describe underwater movement as flying (except metaphorically).
You can probably "fly" at half speed underwater
The rules for swimming ...
As of the 2018 Errata, the Athlete feat has been changed
Athlete (p. 165). The third benefit should instead say climbing doesn't cost you extra movement.
—Errata: Player's Handbook, 2018
Because of this change, the Athlete feat would allow a Centaur to ignore all extra costs associated with climbing. The technicality of ignoring "halved" movement ...
From the section on opportunity attacks:
You can make an opportunity attack when a hostile creature that you
can see moves out of your reach. To make the opportunity attack, you
use your reaction to make one melee attack against the provoking
creature. The attack interrupts the provoking creature’s movement,
occurring right before the creature ...