How do I help my friend make a monster?

[MonkeySage]

I have made my own monsters for other editions, but it seems very difficult for 5e. I tried it before and I was unsuccessful. The creature could not represent the full breadth of abilities I wanted it to have for the scenario.

[Puh Laden]

I have made my own monsters for other editions, but it seems very difficult for 5e. I tried it before and I was unsuccessful. The creature could not represent the full breadth of abilities I wanted it to have for the scenario.

Why not? I don't have a DMG but I've made monsters. I know a monster's CR affects its proficiency bonus, and its hit die is based off of size. And if you don't plan to share it and have it reviewed those don't even matter, just come up with the abilities yourself and do a little playtest using pregens or the party's characters.

Admittedly 5e's sort of half-commitment to monster stats being similar to players but also different with little structure can be annoying, but the bright side is that despite it not being as good as I hear 4e's was it does make it so that you can write down stats you need without the players knowing you didn't make it according to the pre-defined list of abilities because new abilities are expected in home brew.

But back to your problem. What specifically is it? Are you using the DMG to do it or not?

[MonkeySage]

I've only played one game of 5e before, though I'm an experienced 3.X GM and have made creatures for those games in the past, to varying degrees of success. I attempted to make a creature for 5e, partly to see if I could do it. I used the monster manual as the DMG had not yet been published.

As of now, I have the SRD to work off of, and I believe that has content from both the Monster Manual and the DMG.

Here is what my friend had to say about the creature:

The Marabbecca is a common bogey that lurks in inland waters considered dangerous. Spawned from and feeding on the fear of drowning, it lurks in steep lakes and in the bottom of wells. Physically, the creature resembles a hideous anglerfish, with a grasping hand protruding from its forehead and claws on the tips of its fins. It pulls swimmers, waders, and those who are careless near wells down into the water. Lakeshore and river marabbeccas tend to let their half-drowned victims go to spread their frightening stories, while well marabbeccas seldom release their victims, as there will always be those who heard the screams.

In addition to their formidable strength and ability to vanish into the water, they can also manipulate their surroundings. Rivers become more treacherous, the bottom of wells become cavernous, and lake bottoms recede sharply.

According to my friend, they're more dangerous in a fight against someone who is afraid of water.

[BurgerBeast]

I'm on my phone so I can't link the articles, but if you google "The Angry GM 5e monster design" you'll find everything you need in his monster building lab 101 and 202 articles. 202 is where the money is.