Adjusting HP and CR changes

[Stalker0]

I'm planning on doing some small modification to monsters, basically increasing or decreasing their hp by 50% or so. I won't change their HD, just what they are getting for each hd. How much of a CR change do you think this would warrant, especially on the lower 1-3 HD range and higher 6-10 range.

 

[the Jester]

Do you mean you're adjusting the hp rolled by 50% and leaving the con bonus alone, or adjusting the total by 50%?

 

[mikebr99]

If it's just increasing the amount they rolled to near or at max... don't adjust CR at all. YMMV


Mike

 

[Gizzard]

--edit: oops, misread original question ---

Adding HPs is really the same as adding HD. You can calculate how many HPs are expected for HD, HD+1,HD+2 etc. If the new HPs are above the expectation for HD+3 then the monster effectively has HD+3 hit dice.

Here's the rule from the MM for advancing the HD of a Monstrous Humanoid.

Type: Monstrous Humanoid CR: +1 per 3 HD added

So, for example, if the Humanoid had d8, 3d8 expects 13 HPs; so add one CR for every 13 HPs you add to d8 based monsters.

I hope this makes some sort of sense. ;-)

-- double edit ----

Darn, wasn't fast enough to correct myself before someone else caught me being wrong! ;-)

 

[Ankh-Morpork Guard]

This is covered in the MM at the back in a section called "Improving Monsters". You'd have to look up the exact values you are interested in, but heres one just for reference:

Type: Monstrous Humanoid CR: +1 per 3 HD added

Only if you're increasing the HD. If you're just adding HP and not using the average, then I'm not sure it would do a thing.