Monster Advancement.

[Lord Ben]

Can most monsters gain levels? I was looking at formian workers and for advancement it just says 2HD, large. Can it also gain classes?

 

[kreynolds]

Can most monsters gain levels?

Yes.

 

[trentonjoe]

I would say anything with more than a 3 int can gain levels.

As long as you keep adjusting the CR it'll be fine combat balancewise.

 

[Dr. Zoom]

The MM lists the typical way a given creature can advance. Typical formian workers have 1 HD, but some are 3 HD. That does not mean that some cannot advance by character class, it is just not very common.

 

[Lord Ben]

Well, I dislike creatures larger then large. I don't like huge and above and non-humanoids are usually bigger when they get stronger rather then tougher.

 

[Lord Ben]

I would say anything with more than a 3 int can gain levels.

As long as you keep adjusting the CR it'll be fine combat balancewise.

So the listed is how they usually advance right? What about natural armor, ability scores, etc? Do they go up if something goes from 4 to 8 or so?

 

[Christian]

Take a look at the overview section in the front of the MM. Physical attributes, natural armor, and attack damage dice change when the creature's size increases, but not with other advancement. Attack bonus advancement by hit dice is listed in a chart there, and skills and feats will increase for intelligent creatures.

 

[Grazzt]

What about natural armor, ability scores, etc? Do they go up if something goes from 4 to 8 or so?

No. If it advances in size, its traits change. Note however, if you add class levels to a monster, it does gain the ability point increase that players get as they increase in levels.

Also- keep in mind when a monster advances by levels, its monster HD count as "monster levels" (class levels) for purposes of determining overall character level (check the DMG, it is in there).