Need help on monster CR

I've come up with a new monster (actually, stolen from somewhere) to challenge my players with. I'm not sure what the CR would be though. Any thoughts? Critiques would also be appreciated.

Frask
Medium Magical Beast
Hit Dice: 8d10+32 (76 HP)
Initiative: +3
Speed: 50 ft.
Armor Class: 28 (+3 dex, +15 natural)
Base Attack/Grapple: +8/+13
Attack: Bite +13 (1d8+7), 2 claws +11 (1d6+2)
Full Attack: Bite +13 (1d8+7) plus 2 claws +11 (1d6+2)
Space/Reach: 5 ft./5 ft.
Special Attacks: eat magic item
Special Qualities: Darkvision 60 ft. DR 10/adamantine, absorb magic, sense magic.
Saves: Fort +10, Ref +9, Will +4
Abilities: STR 20, DEX 16, CON 18, INT 2, WIS 10, CHA 6
Skills: Survival +11, Spot +11, Listen +11
Feats: Track, Multiattack, Iron Will
CR: 9

This creature resembles a wolf with reflective metallic skin.

Frasks are predators that sense and eat magic for sustenance. Their flesh is made of some sort of metallic alloy that is extremely dense and hard. When they sense magic nearby, they are relentless in tracking it down. When faced with a choice between two targets, they will always go after the one who smells of more magical emanations. Frasks are pack hunters and it is unusual to encounter them alone.

Eat Magic Item: A frask eats magic for sustenance. This can be actively cast spells or magic residing in magic items. A frask can take a full round action that provokes attacks of opportunity to eat the magic bound within a magical item. When it does so, it gains a number of temporary hit points equal to the caster level which was used to create the item. These temporary hit points last an hour. If at any time, the frask has gained a total of 50 temporary hit points from the use of both its eat magic item and absorb magic abilities, it permanently gains a new hit die. In order to use this ability, the Frask must be in possession of the item. It cannot eat an item held or worn by another creature.

Absorb Magic: A frask is immune to any spell or spell-like ability that allows spell resistance. In addition to this immunity, when a frask is subject to a spell that allows spell resistance, it gains a number of temporary hit points equal to the caster level of the spell. These temporary hit points last an hour. If at any time, the frask has gained a total of 50 temporary hit points from the use of both its eat magic item and absorb magic abilities, it permanently gains a new hit die. This ability also means that magical weapons do not gain any of their bonuses against the frask, A +1 flaming longsword would be treated as a masterwork longsword for the purposes of attacking the frask. The frask does not gain hit points from being attacked by magical weapons however.

Sense Magic: A frask can detect the presence of magic near it and uses this sense to hunt. This ability works similarly to detect magic with two exceptions. The frask’s sense extends 60 feet in all directions, and it gains all of the information that detect magic would convey immediately, it does not need to concentrate to gain additional information.

You're pretty close. I'd call it a CR 9 rather than 8, however, because its impressive AC, damage reduction, and spell immunity will tend to drag out a fight, and its ability to destroy items means that it is certain to wreak a lot of havoc during that time.

There are a couple of minor errors in your monster:

You have listed the claws and bite at the same attack bonus, but secondary weapons take a -5 penalty to hit. The attack progression would thus be +14/+8/+8. If you want to optimize the monster, you might consider replacing Weapon Focus (bite) with Multiattack, which would produce a progression of +13/+11/+11.
As an 8-HD monster, this should have three feats, not two. I'd recommend Iron Will for the third feat, to shore up the creature's extremely low Will save.

Also, some questions about the Eat Magic Item ability: does the monster need to be in possession of a magic item to eat it, or can it eat an item worn or wielded by an opponent? If it can eat an opponent's gear, what is the range of the ability? Does the monster need to roll to hit?

A cautionary note about this monster: because of its impressive defenses and the likelihood that the players will inadvertently give it extra hp by casting spells at it, a poorly optimized party might have difficulty harming this monster. However, because of its impressive speed and immunity to magic, they'll also have difficulty running away. You should always be cautious about using monsters that are hard to kill, hard to stop, and hard to escape from, because if the encounter proves tougher than expected, the PCs pretty much have to just take their beating.

Quote:

Originally Posted by jiriku

You're pretty close. I'd call it a CR 9 rather than 8, however, because its impressive AC, damage reduction, and spell immunity will tend to drag out a fight, and its ability to destroy items means that it is certain to wreak a lot of havoc during that time.

Yeah, CR 9 will probably be a better fit.

Quote:

Originally Posted by jiriku

There are a couple of minor errors in your monster:

You have listed the claws and bite at the same attack bonus, but secondary weapons take a -5 penalty to hit. The attack progression would thus be +14/+8/+8. If you want to optimize the monster, you might consider replacing Weapon Focus (bite) with Multiattack, which would produce a progression of +13/+11/+11.

Right you are. I always seem to forget that for some reason.

Quote:

Originally Posted by jiriku

As an 8-HD monster, this should have three feats, not two. I'd recommend Iron Will for the third feat, to shore up the creature's extremely low Will save.

I'd say that if it needs to be in possession of the item, that makes it a far weaker threat than otherwise (since it has no good way to get said possession), but still probably a CR 10 or 11 (assuming a party for which most CRs are appropriate) simply because before that it's too difficult to get past both its extremely high (for lower levels) AC and its DR. The only reason it's not higher is because its attack is pretty weak for even that CR.
If it got Improved Disarm or some other way to steal magic weapons, I'd give it a CR of at least 14 or 15.

Quote:

Originally Posted by jiriku

You're pretty close. I'd call it a CR 9 rather than 8, however, because its impressive AC, damage reduction, and spell immunity will tend to drag out a fight, and its ability to destroy items means that it is certain to wreak a lot of havoc during that time.

There are a couple of minor errors in your monster:

As an 8-HD monster, this should have three feats, not two. I'd recommend Iron Will for the third feat, to shore up the creature's extremely low Will save.

of course, as its immune to most magic... what else requires a will save?

and why is the armor class so ridiculously high? Its put up their by natural armor twice as effective as plate --- and has damage reduction on top of it. It seems like a good way to extend an encounter-- hard to hit, hard to damage when you hit (really, how are you going to dammage it? magic doesn't work, including dammage, and power attacks won't hit it, yet it can't really tear the charactar apart.

then again, the best response is a dog pile. buff the fighter up, and have him pin the thing, maybe throw someone else on there as well. I don't know if you realized thats its weakness.

It is weak aginsts SR: no, touch attack spells, but other than those it would be rather hard to kill at level 10(unless the group has an adamant weapon wielding high str character[really high str, 26+(for a +8 bonus to attacks)])

Maybe tune down the A.C and damage resistance a little?

or break out the ~~chainsaw~~ shameless plug.

Quote:

Originally Posted by Togath

[FONT="Book Antiqua"][SIZE="2"]It is weak aginsts SR: no, touch attack spells

True, but there are something like only 2 of those (and one a cantrip) available before extremely high levels, assuming whoever's playing it doesn't have more than Core. So if he hasn't prepared Acid Arrow that day, you're in trouble.

And an enemy that can't be beaten with just Core (plus campaign-specific homebrew) is too powerful except for use on a case-by-case basis.

I think with Absorb Magic the question is: can a 9th level fighter have an okay chance to do that thing on his own? Because then, it should be fair for party with a rogue in addition and casters to buff that fighter.

For fun, I just created a fighter.

The fighter and the "average fight" against the Frask in spoiler. A bit long and probably not interesting for everyone:

Spoiler
Show

Durin the 9th level Dwarven Fighter:

Feats: Dodge, Mobility, Spring attack, Combat Expertise, Improved Trip, Power Attack, Weapon Focus, Weapon Specialization, Greater Weapon Focus

Attacks: Guisarme: 9+4Str+2feat+2bonus : +17/+12 for 2d4+10 /x3
(Armor Spikes: +14/+9 for 1d4+4 /x2)
AC: 10+10AC+1Dex+1Dodge+1insight+2Nat+3def = 28
HPs: 9d10+45 = 99
Saves: 13/7/5

Expandables:
2 Tanglefoot Bags
Potions: Invisibility, 5x Cure light wounds, Shield of faith +3 (Included), Blur

Ye olde Spring attack/reach weapon fighter.
And an old fashioned dwarf wields no fantastic chain like a biker, if there are good old polearms available.

I'm taking average circumstances: The fighter has an idea of his opponents strengths and weaknesses but does not have an adamantine weapon.

The fight:
The two combatants see each other from some distance, enough for Durin to wet his pants or dring his potions of Shield of faith +3 and Blur.

Durin starts the fight with a tanglefoot bag. In 1/4 all cases the Frask is glued to the ground and needs about 2 rounds to break free. But the Frask has -2 attack and -4 Dex and half speed, what was the idea of it. With boots of speed, Durin has a slight speed advantage which he uses to get his first spring attack in (from distance back to 15 ft distance)
He uses a moderate 2 Combat expertise 2 Power attack, knowing that the monster has both Natural armor and Damage resistance.
+13 vs. 28-2 AC : 40% hit chance for 2d4+4 damage (average 5).
The Frask angrily ~~attacks~~ charges and suffers an AoO for his movement. Durin estimates that trip attacks might not work that goos against a strong 4-legged creature (actually, it's +17 vs +17) and attacks again, this time for 50% hit prob.

The Frask bites with +13+2-2 vs AC 30 : 20% hit for 1d8+7 damage (average 11.5) 20% of all hits are negated by the Blur potion.

After a few rounds, Durin will notice, the Frask hit's bad but not "nat 20"-bad, yet and goes to Combat Expertise 5, reducing the Frask's hit% to 5%, 15% after the two tanglefoot bags (always charges). He hits 35%, 25% later (he chooses not to change power attack (down to 25%/20% would be better, but he has only a rough knowledge of the damage reduction so he does not know)

So, let's count the HPs.

10 rounds tanglefooted:
Durin average 2 * 0.35 *5 = 3.5 damage.
Frask average 1 * 0.05 * 11.5 *0.8 = 0.46 damage

Afterwards:
Durin average 2 * 0.25 *5 = 2.5 damage.
Frask average 1* 0.15 * 11.5 *0.8 = 1.38 damage

At 25% HPs Durin 5ft-steps, drinks invisibility, followed by runs/moves to get out of sense magic range, then 5d8+5 = 25.5 hp from the cures.

So they have: Durin 124.5 hp, Frask 76 hp.

Thus, Durin needs 26.4 turns in average to kill the Frask (not counting the invisible rounds, only those he attacks)
The Frask needs 86.88 turns in average to kill Durin.

I think it's pretty sure, who you place your bets on here. Two levels down, let me estimate ... Durin's effective damage output should halve while that of the Frask doubles, considering equipment, feats and BAB.
Now with 53 vs. 43 turns (rough estimate), this is "some chance" for the fighter but with a little luck, maybe one or two lucky criticals, he could do it.

Now at level 7 buffed also with Aid, Enlarge person, Bull's strength and Heroism and possibly with a flanking buddy, or conjurations that allow no spell resistance, I see clearly enough possibilities. Not exactly save (for example: What if the fighter of the group dual-wields?), probably, but still I say:
Definitly no CR 9. Either a weak 8 or a strong 7.