Are there rules/guidances for making weaker monsters?

Question

I am aware there's documentation for Improving Monsters but I was curious if there's documentation/rules/guidances for making weaker monsters than their default stat blocks.

Specifically, I was mulling that many monsters grow (are not created immediately with the stats (specifically HD) in the stat blocks), for easy (and real) example: humanoids and animals. They could be in a combat either designed (to go easier on lower level parties) or because they exist and are attacked.

NOTE: I could make up rules for this, but am curious if there are existing ones; I don't desire someone's homebrew solution.

Another answer I was mulling was that younger versions just aren't meant to be in combat. I actually recall (but did not find, nor am I sure if it was a rule or just author discretion) a module where a group of lizardfolk children (and women!) were non-combatant (no stat block) and there was a moral dilemma if the party should just slaughter them or leave them alone. This is especially interesting to me because the typical lizardfolk is 2HD so there (conceptually) easily could be a "weaker" 1HD version.

I think for another example, a baby hill giant could do some damage to a level 1 character. Even kittens can scratch.

Answer 1

Whilst I'm not aware of any 3.5 templates or rules that you could apply in this situation, Pathfinder has the 'Young' template which should do what you need and is easily portable.

Pathfinder simple template: Young (CR –1)

It comes with a set of 'Quick' rules for using on the fly:

Quick Rules

+2 to all Dex-based rolls, –2 on all other rolls, –2 hp/HD.

And a set of more complete rules for rebuilding the stat-block completely:

Rebuild Rules

Size decrease by one category; AC reduce natural armor by –2 (minimum +0); Attacks decrease damage dice by 1 step; Ability Scores –4 Strength, –4 Con, +4 size bonus to Dex.

Answer 2

There is a 3rd edition solution: the book Savage Species. While the goal of the book is to allow players to play weaker versions of high-powered monsters starting at level 1 and "level up" the monsters until they reach the "normal" monster power level (after which normal class levels can be added), it can just as easily be used to de-power a monster to whatever level you want. In addition to having many Monster Manual monster progressions in the book, it also details how you, as a DM, can perform the calculations yourself on any monster.

Since this is a 3.0 book, you may need to tweak the progressions of any monsters that have changed between 3.0 and 3.5.

Answer 3

You could try using Dungeonscape's Dungeonbred template to size animals down to be younger versions of the base.