Monster Design Questions

[Rossbert]

I am starting work on my first 5e monster (well a progression of three monsters) and was looking for some guidelines.

Is there a recommended progressin of Hit Dice and damage by CR?
Should there by a limit to the number of special abilities a monster has?
What is a good way to determine AC?

 

[plisnithus8]

"Creating a Monster" DMG p. 273

 

[Rossbert]

Silly me, looking in the MM.

 

[Rossbert]

I hope to have a rough draft of at least one of three (probably the lowest powered one) up in a week or so, depending on family and work.

 

[Ranthalan]

Would love to see what you come up with.

 

[dave2008]

I am starting work on my first 5e monster (well a progression of three monsters) and was looking for some guidelines.

Is there a recommended progressin of Hit Dice and damage by CR?
Should there by a limit to the number of special abilities a monster has?
What is a good way to determine AC?

The DMG has a Monster stats by CR table in the section on making / modifying monsters. You can find the table with a google search; however, you probably will not find the information needed to fully use the table (what modifies things) without the DMG.

The number of HD don't have a simple relationship to CR / monster difficulty in 5e like some older editions. Since HD also takes in size (d4/d6/d8/d10/d12/d20) as well as progressively more HD

It is usually best to keep special abilities to a few distinctive ones if this a creature to be killed quickly. If it is a recurring or legendary threat then more traits and abilities help keep it interesting. Look through the MM for examples, but I tend to give monsters more traits than what is found in the DMG.

AC is 10 + Dex bonus, unless it has natural armor (like dragons), or is wearing armor (in which case use the AC for the armor). If it has natural armor, you can make the AC based on what you think it should be like (is this monster's hide as tough as scale or plate armor?) or you could use the Stats by CR table to give you an idea of where the AC should be.

 

[Rossbert]

It is probably going to overloaded with abilities, at least until the drafts get checked. HD and HP are a struggle.

 

[Harzel]

Be aware that for monsters with CR less than 2, the table of monster stats by CR is extremely misleading in the sense that if you stat a monster that you intend to be, say, CR 1/2, by just taking values from the line in that table for CR 1/2, the monster will be much tougher than any of the CR 1/2 monsters in the MM. Most of the lower level monsters in the MM are built with a (relatively) high offensive CR and a (relatively) low defensive CR, and a lot of the higher level monsters are as well. Unless you follow this pattern, your creature's actual power may well be very different from that of creatures in the MM with the same CR.

Since the CR calculation involves a table with multiple disparate monster characteristics and a multi-step calculation, it's hard to point to any one thing and say that that is what is off. However, the fact that for CR 1/8 the HP range is 7-35, whereas higher CR values have HP ranges with a max-min difference of 14 tells you that something is whacked.

 

[Rossbert]

Quick aside, what damage type would people consider being sucked against a small opening by a strong vacuum or wind? Bludgeoning?

 

[Afrodactyl]

Probably bludgeoning.

As far as guidelines for statting a monster, I generally choose a monster that's around the same size and toughness as what I want to end up with and just tweak the numbers slightly. Hobgoblin warlords with different gear make for mean humanoid bosses at lower levels. Tweaked trolls are another favourite of mine.

But yeah, if in doubt, check the DMG. You can find CR calculators online that will give you a rough idea of what your CR will be as well.