So I was looking at miniatures on etsy and came across a Cerberus Rex (Basically a 3 headed Tyrannosaurus) I immediately want to use it so I looked at stats of both creatures. The Rex being a 9 and the Cerberus being a 23 ;
(3rd party; it has a laundry list of other powers to justify it)
How I would do it just add two bite attacks and maybe a rend if 2 bites connect. I think it should raise its CR but by how much is where I am curious. Maybe a +2
I would give it two more bite attacks, Pounce, and Fast Swallow... probably up the CR to around 12?
I don't disagree with Mark, but considering that the Tyrex bite deals an average of 35.5 dmg per hit, discounting any critical, i feel like adding two extra bite is worth +2 CR.
According to the monster creation table, the Tyrex as a bonus to hit of roughly a CR 11 creature, but the damage of a CR 8. If we had two extra bite, this bumps the damage to CR 18-19, which is pretty significant.
His defensive capabilities aren't also too terrible. The Tyrex has hp equal to a creature of CR 11-12 and the AC of a CR 8. It's saving throws are around CR 11-12 as well.
However, the tyrex being dump as a brick should be factored into it's CR, and probably already is, any party that has access to mobility magic can totally ignore or destroy the poor dinosaur.
I don't know how much of a ''cerberus'' creature you wanna make it, but maybe it could breath fire like a hellhound? That way it would give it a bit of ways to deal with flying creature, which at CR 10-11 would be vital.
Without pounce, it's not that much more of a threat. Without flight or ranged attacks, it's still very weak to the typical method of nullifying the encounter. Flying above and slowly killing it from safety can be prevented, but if there isn't something in place to prevent it, I'd maybe increase the CR by 1. I wouldn't expect it to perform better, but I'd adjust the reward for the players since punishment for bad tactics is a little higher.
If you gave it DR against ammunition attacks, a high jumping pounce, good stealth, some knock from the sky and knock prone like abilities, then you could worry more about that full attack damage bump.
If it had high synergy allies, like a 5th level wizard friend that casts fly and invisibility on it, I'd boost the encounter CR by 2 rather than 1.
I jumped it up CR +3, for some ungodly reason, but I added fast swallow, the Morlock's leap attack, and pounce... gave it Vital Strike as a bonus feat, and a racial bonus to Acrobatics for jumping. It already has the run feat, which I factored into its skill bonus even though it would be 4 less without a running start. What-TF-ever. Lol.
Could have just added 1HD for the feat slot to grab Vital Strike without a bonus feat, but I was too lazy to recalculate all that manually.
3-headed Tyrannosaurus CR 12
XP 19,200
N Gargantuan animal (magical beast?)
Init +5; Senses low-light vision, scent; Perception +37
DEFENSE
AC 21, touch 7, flat-footed 20 (+1 Dex, +14 natural, –4 size)
hp 153 (18d8+72)
Fort +15, Ref +12, Will +10
OFFENSE
Speed 40 ft.
Melee 3 bites +20 (4d6+22/19–20 plus grab)
Space 20 ft.; Reach 20 ft.
Special Attacks fast swallow, leap attack, pounce, swallow whole (2d8+11, AC 17, hp 15)
STATISTICS
Str 32, Dex 13, Con 19, Int 2, Wis 15, Cha 10
Base Atk +13; CMB +28 (+32 grapple); CMD 39
Feats Bleeding Critical, Critical Focus, Diehard, Endurance, Improved Critical (bite), Improved Initiative, Iron Will, Run, Skill Focus (Perception), Vital StrikeB
Skills Acrobatics +22 (+34 to jump), Perception +37;
Racial Modifiers +8 Acrobatics (to jump), +8 Perception
SQ powerful bite
SPECIAL ABILITIES
Leap Attack (Ex)
As a standard action, a 3-headed tyrannosaurus may make a single attack during a jump. It can make this attack at any point along the course of the leap—the start, the end, or while in mid-air. While jumping, a 3-headed tyrannosaurus does not provoke attacks of opportunity for leaving a threatened square. A 3-headed tyrannosaurus always considers Acrobatics as a class skill and has ranks equal to its HD.
Powerful Bite (Ex)
A 3-headed tyrannosaurus applies twice its Strength modifier to bite damage.
Without pounce, it's not that much more of a threat. Without flight or ranged attacks, it's still very weak to the typical method of nullifying the encounter.
While that's true, martials are still gonna bite it, its still very dangerous to melee. The basic Tyrannosaurus is strong, but not too dangerous to go up against in melee because it's limited to one attack. If we typically acknowledge the fact that adventurers tend to fight creature 3 cr above them, dishing out 110 damage average damage in a turn is a significant bump. Most adventurer of 8 to 9 will get destroyed if it gets a round. Of course, it's CR can be totally nullified by flying high enough and shooting it down with a bown. That's asumming it's possible, as it could be met in a closed temple, or somewhere where such tactic is hard to pull off.
I think VoodistMonk version is nice, although very scary. With +5 initiative, pounce and fast swallow, it's like a dire tiger on steroid. With 3 attacks at +22 on a charge, 130 average damage in a round, it's a destroyer of adventurer. CR 12 seems appropriate though as it can't do much more else. The plus side is that this thing has -11 in stealth so it should be obvious from afar.