Monster Advancement and CR

[wolff96]

I've been looking in the SRD, but I can't find the passage I need. My books are at home. So if anyone can answer this, I'd really appreciate it.

When you advance a monster -- not by class levels, but by hit dice -- what is the rule for advancing the monster's CR?

 

[Tiberius]

IIRC, the CR remains the same regardless of how much the creature advances via HD increases. Though I am working off of memory and could be very wrong.

-Tiberius

 

[Caliban]

I've been looking in the SRD, but I can't find the passage I need. My books are at home. So if anyone can answer this, I'd really appreciate it.

When you advance a monster -- not by class levels, but by hit dice -- what is the rule for advancing the monster's CR?

According the MM errata, for every 50% increase in HD, it's +1 to the CR.

This should be considered a rough guide at best, as it breaks down with very small or very large monsters, or monsters with a lot of odd special abilities.

 

[wolff96]

Re: Re: Monster Advancement and CR

According the MM errata, for every 50% increase in HD, it's +1 to the CR.

This should be considered a rough guide at best, as it breaks down with very small or very large monsters, or monsters with a lot of odd special abilities.

First off, thanks for the response. I appreciate the information.

I'm not sure that WoTC's system seems right to me, though. For plot reasons, I have a 36 HD Fiendish Tyranosaurus. Since the base creature is 18HD and a CR 8, that makes a 36HD Fiendish version a CR of 12! For a monster with one attack at (if my math is right) +35 that does 10d6+19... And a once a day Smite for an extra 36... Yikes.

And it shouldn't be a push-over at 522 HP (and that's AVERAGE).

Hmmm. I think I'm going to have to modify that CR rating. It just seems really low to me. Granted, flight could really trivialize the encounter, but...

 

[Grazzt]

Re: Re: Re: Monster Advancement and CR

First off, thanks for the response. I appreciate the information.

I'm not sure that WoTC's system seems right to me, though. For plot reasons, I have a 36 HD Fiendish Tyranosaurus. Since the base creature is 18HD and a CR 8, that makes a 36HD Fiendish version a CR of 12! For a monster with one attack at (if my math is right) +35 that does 10d6+19... And a once a day Smite for an extra 36... Yikes.

And it shouldn't be a push-over at 522 HP (and that's AVERAGE).

Hmmm. I think I'm going to have to modify that CR rating. It just seems really low to me. Granted, flight could really trivialize the encounter, but...

I would set it around CR 21 or 22 myself.

 

[Numion]

Re: Re: Re: Re: Monster Advancement and CR

I would set it around CR 21 or 22 myself.

A big stupid creature can have gazillion HPs, and still not be much of a threat for 12+ level PCs. Clearly this T-rex is dead meat if it enconteurs a party that can for example fly. Not an idea unheard of at levels 10+.

It follows that any creature that can't fly, is stupid and has no special abilities should almost never have a CR of 16+. IMHO, of course. Not so HO actually, cause I've seen high-level groups grind big stupid creatures into pulp with little harm to themselves.

Fiendish T-rex has even low will save. (+14 with 36HD). Single hold monster will kill it.

CR 21-22? Seriously?

 

[Crothian]

Re: Re: Re: Re: Re: Monster Advancement and CR

Take a look at the Collassal Scorpion and it's CR. It's going to be about as tough as the creature being proposed. If you get caught in melee with it, one is going to get killed. But they have very little ability to deal with a smart, resourceful party.

CR 12 sounds about right.

 

[Grazzt]

Re: Re: Re: Re: Re: Re: Monster Advancement and CR

Take a look at the Collassal Scorpion and it's CR. It's going to be about as tough as the creature being proposed. If you get caught in melee with it, one is going to get killed. But they have very little ability to deal with a smart, resourceful party.

CR 12 sounds about right.

Not quite. The Fiendish t-rex is slightly deadlier than a common Colossal scorpion (and by common, I mean no templates or alterations to its stats in the MM).

Colossal scorpion only has 416 hp. His fiendish t-rex detailed above has 522 hp. Using the WotC CR guesstimator (Dragon 276 or my site) this automatically puts its CR above the Colossal scorpion's CR by a few points.

Also- Fiendish automatically adds to the CR (in this case a +2).

Fiendish t-rex has : improved grab, swallow whole, scent, smite good, darkvision 60 ft, cold and fire resistance (20), damage reduction 10/+3, SR 25

Colossal scorpion has: improved grab, squeeze, poison, vermin


If you use the CR guesstimator that WotC published the Colossal scorpion actually comes out to be way higher on the CR scale than it is listed.

Colossal Scorpion:

1- avg hp/4.5: 416/4.5 = 92.4
2- add +1 or +2 for each SA and SQ: +1 for poison, +1 for improved grab, +1 for squeeze, +1 for vermin = +4 total. So total result is 96 (92.4 + 4)
3- Divide result by 3 to get CR: 96/3 = 32

Obviously it isnt listed at CR 32, but using the guesstimator there ya go.

Now for the Fiendish t-rex:

1- 522/4.5 = 116
2- +1 improved grab, +2 swallow whole, +1 scent, +1 smite good, +1 darkvision 60 ft, +2 cold and fire resistance (20), +2 damage reduction 10/+3, +2 SR 25. Total bonuses = +12. Total result is 128.
3- 128/3 = 42

So- slightly more powerful.

Perhaps CR 21 or 22 is too high. If you divide by 32 by 2.909 you will get the CR 11 the colossal scorpion is listed as. Divide the 42 (for the fiendish T-rex) by 2.909 to get CR 14 (then add +2 for the Fiendish template).

So- CR 16 sounds better.

 

[Earthstone]

good work, 16 sounds good