There are no general rules for digging speed
There are no general rules for how quickly characters can dig, whether they're doing a proper excavation from outside the hole or if they're trying to dig themselves out of a grave.
Other answers have fairly pointed out that the realistic effect of being shoved into a hole and having a five foot cube of dirt ...
Under the condition that the GM decides that it works as depicted by OP:
He's dead Jim
Sorry to break this to you, but the character will be squished by up to 11.8125 metric tons (~13 US tons) of loose dirt the moment the spell Mold Earth releases the grasp on the ground: That excavated cube is about 3.375 m³. The heaviest rocks have a density of about 3.5 t/...
The fancy unconscious/initial dig is not that important. Arguably the PC was awake after being dropped 5' into a pit, but prone, as being pushed 5' by wind then dropped 5' is a lot more impactful than a slap, and definitely shakes the creature.
So the question becomes, there is a creature prone in a 5' square pit. Someone uses mold earth to bury them. How ...
First we need to determine the Grease spells area:
Slick grease covers the ground in a 10-foot square centered on a point within range
Then we need to determine what "enters spell area" means. I did not find clear definition, but if you fly over the area of Grease spell, it'd take a special kind of DM to consider that "entering".
Consider the situation:
Here, our big red creature moves five feet south. I repeat, our big red creature moves 5 feet south.
If the creature had 30 feet of available movement before the move, the creature has 20 feet of available movement after the move (movement cost is doubled for difficult terrain). No one is going to argue that (30-20)/2 is ...
The creature would need a Strength score of 11 and 21 movement speed.
The jumping rules state
When you make a long jump, you cover a number of feet up to your Strength score if you move at least 10 feet on foot immediately before the jump.
And Grease is a 10ft area on the ground. A creature that flies, hovers, jumps, or otherwise is able to avoid the ...
The spell says:
… move as far as its speed allows away from you …
There will be a place(s) that is “as far as its speed allows” that involve approaching the caster to get there - that place(s) would be legitimate aiming points if “away” only applies at the end of the move. Which supports your interpretation.
But is also ambiguous. Because “...
Earthbind disables a creature's fly speed and describes the speed at which the creature descends.
Earthbind does not drag creatures down, it simply makes them begin falling. Creatures affected by it would normally fall, so it sets limits for how fast affected creatures can fall.
The creature would fall to the point it normally would under any other falling ...
Mold Earth - A cantrip, probably the easiest way to make difficult terrain but it's only 5ft at a time.
Bones of Earth
Investiture of Ice
Storm of Vengence
Wall of Water
The character is dead.
Based on this reference, the lower end for the weight of a cubic foot of soil is 74 pounds. The character is buried under 125 cubic feet of soil, or at least 9250 pounds of soil. But let's be more conservative - the character is not 5 feet by 5 feet. Suppose the soil directly above the characters body is more like 2 x 5 x 5 feet, or 50 ...
In 5e grids are an optional rule, the rules don't assume you are playing on a grid leading to awkward situations. The movement rules are no help, they just say "you can move a distance up to your speed". The difficult terrain rules say "Every foot of movement in difficult terrain costs 1 extra foot. This rule is true even if multiple things in ...
In this situation, you cannot move
When moving on a grid, movement is measured in squares; to enter a space that costs four times as much movement, you must have four squares of movement available.
The rules on Playing on a Grid state:
Squares. Each square on the grid represents 5 feet.
Speed. Rather than moving foot by foot, move square by square on the ...
Based on the interpretation of
The creature doesn’t move into obviously dangerous ground, such as a fire or a pit.
there is an argument to be made that moving into an area where you are trapped and can’t escape could be construed as “obviously dangerous ground”. Additionally, because the spell doesn’t explicitly inflict the “frightened” condition, ...
No, because of what a saving throw represents
As Dale M points out, the spell text relating to the forced movement itself is unfortunately ambiguous, and either interpretation is possible.
So let's look at the part of the spell that AncientSwordRage did not quote:
You whisper a discordant melody that only one creature of your choice within range can hear, ...
It's not made explicit, but it's confirmed by other rules.
As you yourself quoted in the question, the guarded step rules text does not say anything about difficult terrain. It only says that you can move 5 feet as a move action, while the difficult terrain rules say that it takes two squares of movement to move into a square of difficult terrain. Since a ...
Although the rules interaction isn't explicit, the two rules combine together. Difficult terrain doubles the cost of moving into the terrain. Therefore, a 5' move is not enough to crawl into it. The Crawl move action also gives 5' of movement, and would similarly not allow one to crawl into a square of difficult terrain.
Under Movement and Position is a ...