I'm fairly new to D & D 5e, but I've played some Pathfinder and 3.5e, so I have some experience with D & D. We are playing our current game in 5e according to the rules as they are written.
Our DM made our group meet a Mezzoloth (MM, p.313) with 3-4 other guys two sessions ago. We are at level 6.
We fled because we did not prepare enough for the fight, and the ground was working again. At some point later, he launched a cloudkill spelling to us and almost everyone died, so we fled.
In the last game, we found the new location of the same Mezzoloth and decided to kill it, since the terrain was our advantage this time (they were in a small room).
The fight was strange, and I felt a little deceived by the way the DM played the Mezzoloth.
First question: Approximately 16 hours passed between our two meetings. How does the cloudkill spell works? The statblock says that the mezzoloth can cast it "1 / day". Does this mean that it resets at midnight, or does it have to wait 24 hours between each use?
Second question: Can you see blindly / see through the doors?
When we were about to open the door and surprise them, there was a darkness Spell ready for us in the room. I think it was impossible for the monster to know at what exact moment we would open the door. (They saw us camping in a small hut 6-7 hours ago near their new hiding place, and we did not see them again after that.) Darkness it only lasts 10 minutes; How could they know when to launch it?
In addition, an additional question: can the blind view or the vision of the truth see within the small hut spell out?
Third question: The Mezzoloth that we fought with could, in the same turn, use their Teleport action and then attack, or use magic (as dispel magic) and then attack. How do I understand the Monster manual, a monster acts as a player character, and I can not see in the block of monsters how I could do both actions in the same turn (nothing appears as a bonus action or whatever) Is it legitimate?
Our DM said that the teleport was part of their movement, but I can not find any documentation about it. I myself want to start a D & D 5e game in the future, and I'm pretty curious about how to play monsters.
And finally, just to be sure: One of our characters used the action of dealing and in some way incapacitated the mezzoloth (with a single successful grip roll); He said he was jumping in the throat of the mezzoloth and got a good score.
Based on my reading of the rules, the staple condition does not do that; simply reduce the creature's speed to 0. Did we just fold the rule for an impromptu action? Is it legitimate?
At this point, I just closed my mouth; I was tired of this crazy fight and I wanted the mezzoloth to die.
I do not understand the rules or are we playing badly?