D&D 5E Grappling & engulfing - how do they work in 5e?

[crashtestdummy]

how about cast Misty Step? (Lvl 5 Paladin) - will this not work because I'm blinded?

Misty Step
Conjuration

Level: 2
Casting time: 1 Bonus Action
Range: Self
Components: V
Duration: Instantaneous
Briefly surrounded by silvery mist, you teleport up to 30 feet to an unoccupied space that you can see.

If you're blinded, you can't see, which means you can't use Misty Step.

 

[Flamestrike]

Multiattack: The shambling mound makes two slam attacks. If both attacks hit a Medium or smaller target, the targetis grappled (escape DC 14), and the shambling mound uses its Engulf on it.

Slam ­ Melee Weapon Attack: +7 to hit, reach 5 ft., one target.Hit: 13 (2d8 + 4) bludgeoning damage.

Engulf: The shambling mound engulfs a Medium or smaller creature grappled by it. The engulfed target is blinded,restrained, and unable to breathe, and it must succeed on a DC 14 Constitution saving throw at the start of each of themound’s turns or take 13 (2d8 + 4) bludgeoning damage. If the mound moves, the engulfed target moves with it. Themound can have only one creature engulfed at a time.

If it hits you with both slams you are automatically grappled, blinded and restrained (and unable to breathe).

At the start of your next turn you must pass a DC14 Con save or take 13 points of bludgeoning damage.

During your turn you can:

a) Attack the mound (at disadvantage thanks to being restrained and blinded) Many DM's will require such an attack to be with a light weapon such as a dagger (this last bit is DM dependent)
b) Attempt to escape (DC 14 Strength [athletics] or Dex [acrobatics] check) in place of an attack.
c) Cast a spell that doesnt require sight (so no misty step, targetted spells etc)

You cant make opportunity attacks while engulfed (these require LOS). You cant cast most spells (LOS again). You cant move (your speed is zero). Technically attacks against you have advantage, but youre engulfed, so its likely total cover and thats probably not an option (DM dependent).

You also have disadvantage on dex saves, but again youve probably also got total cover (from the mound).

Youre stuck inside the thing until you break out, or it kills you.