what is this CR of this golem?

[dungeon blaster]

ADAMANTINE GOLEM
An adamantine golem cannot speak or make any vocal noise, nor does it have any distinguishable odor.
An adamantine golem’s natural weapons are treated as adamantine and magical for the purpose of overcoming damage reduction.

Adamantine Golem
Large Construct
Hit Dice: 25d10+30 (167 hp)
Initiative: +0
Speed: 30 ft. (can’t run)
AC: 36 (–1 size, +27 natural)
Base Attack/Grapple: +18/+37
Attack: Slam +33 (3d10+16) melee
Full Attack: 2 slams +33 (3d10+16) melee
Space/Reach: 10 ft./10 ft.
Special Attacks: Trample (4d10+24), disjunction
Special Qualities: Construct traits, darkvision 60 ft., low-light vision, true seeing, magic immunity, DR 20/magic and adamantine
Saves: Fort +8, Ref +8, Will +8
Skills: Jump +14
Abilities: Str 43, Dex 11, Con –, Int –, Wis 11, Cha 1
Climate/Terrain: Any land
Organization: Solitary
Challenge Rating: ??
Treasure: None
Alignment: Always neutral

Combat
Trample (Ex): As a standard action during its turn each round, the adamantine golem can literally run over an opponent at least one size category smaller than itself. The trample deals 4d10+24 points of bludgeoning damage. Trampled opponents can either attempt attacks of opportunity at a –4 penalty or Reflex saves (DC 38) for half damage. The DC is Strength-based.

Magic Immunity (Ex): An adamantine golem is immune to all magical and supernatural effects.

Disjunction (Sp): An adamantine golem can cast mage’s disjunction as a spell-like ability three times per day at 25th level of ability.

True Seeing (Sp): An adamantine golem has a true seeing spell always in effect. The effect can be dispelled, but the golem can reactivate it as a free action.

 

[Shade]

I'd place it around CR 16. I used an iron golem (CR 13) as the base, and added +1 for extra HD, +1 for the disjunction ability, and +1 for total immunity to magic. I might be tempted to add another +1 for the very high Str score.

 

[Sigurd]

Two things

I think that Golem immunities have changed in 3.5. They are now only immune to magic that offers a saving throw.

How much do you think this Adamantite thing weighs. The quantity of adamantite might be the biggest treasure in your adventure

S

 

[Knight Otu]

I think that Golem immunities have changed in 3.5. They are now only immune to magic that offers a saving throw.

Spell resistance, actually.
A scaled-down adamantine golem, -29 HD and Large. Using the advancement guidelines in reverse, we get about CR 17. 16 or 17 should be about right, I think.

 

[dungeon blaster]

Yes, it is a scaled down ELH adamantine golem, with disjunction and true-seeing ability. Also, it has DR magic and adamantine instead of epic and adamantine. The original golem did base 6d10 damage, I have no idea what it should do as a size category smaller...any idea? I figure that the disjunction has gotta add at least +1 CR. I am also thinking of allowing its creator to possess it, much like how a magic jar spell works.

Hmmm...what if its slam attacks cast greater dispelling? That would be pretty wicked.

It is actually composed of iron polymorphed into adamantine. When the golem is destroyed, it would probably turn back to regular old iron.

 

[Shade]

The improving monsters table doesn't really address d10s, but you could use the decreasing weapons table from the Arms and Equipment Guide. By those rules, d10s decrease to d8s for one size decrease, so you could have it deal 6d8 damage.