Help with a CR

[Icewalker]

Medium Construct
HD 1d10+20 (25)
Speed 30 ft. (6 squares)
Init: +0
AC 13 (+3 Natural)
BAB +0; Grp +0
Attack Inflict Light Wounds (+0 to hit on touch attack)
Full-Attack Inflict Light Wounds (+0 to hit on touch attack)
Space 5 ft.; Reach 5 ft.
Special Attacks Inflict Light Wounds (1d8+1) Will save DC 13
Special Qualities Hardness (DR/adamantine) 1
Saves Fort +0 Ref +0 Will +2
Abilities Str 10, Dex 10, Con -, Int -, Wis 14, Cha 6
Skills
Feats
Environment
Organization Single
CR ?
Treasure None
Alignment Neutral

This is a construct I am going to use at some point, and I'm not sure what the CR is. It is supposed to be a fight for a first level party which they should be able to win, but it will be hard (it is a punishment if they screw something up).

I'd like to note that the party may have a slightly higher number of arcane casters than a usual party.

changes so far in blue.

[Kyace]

BAB +1; Grp +2
Attack Inflict Light Wounds (+1 to hit on touch attack)
Full-Attack Inflict Light Wounds (+1 to hit on touch attack)
Space 5 ft.; Reach 5 ft.
Special Attacks Inflict Light Wounds (1d8+2) Will save DC 13
Special Qualities Hardness (DR/adamantine) 2
Saves Fort +0 Ref +0 Will +2
Abilities Str 10, Dex 10, Con -, Int -, Wis 14, Cha 6

Crunch-wise, Its better to deal 1d8+2 with a spear and 14 Str than with touch spell that then requires a will save; unless you have a compelling fluff reason not to, I'd just give your Construct a Slam that deals 1d8+Str bonus. Besides, a construct that can constantly casts Inflict Light Wounds is very likely to be broken by evil clerics: they capture the construct and keep it in a cage, whenever an undead needs healed, they put it in the cage too and the construct, according to its programming, "attacks it", healing it.

As for CR, I'd currently give it a CR of about 2 or 3; due to sheer number of HP it has it can last long enough against your party that someone might get hurt. If you replace the Inflict Light Wounds with a normal melee attack, I'd guesstamate that it'd be roughly a CR of 3.

Now, for your party, I'd say this: unless they have some heavy damage dealing capability, a level 1 party may be walked over by this construct. Rogues and wizards are fragile at level 1 and both are weak against constructs in general and especially against constructs at level one. Your party will be very dependent on its melee's damage dealing ability to defeat this. If they lack such a character, they will likely be unable to defeat this.

To make this more friendly for a typical level 1 group, I'd make the construct small and only have 1 HD and 4 Natural Armor: this halves the HP from 31 to 15 while keeping the AC and the to hit the same. This would still be a CR 2 encounter, but its be more survivable for the party.

[DracoDei]

The advantage to Inflict spells is that they ignore armor/natural armor (and DR, but that isn't going to be an issue for 1st level characters).

[Kyace]

A touch spell with a will save at first level seems like a bad trade: the couple of AC you ignore is then rendered pointless by make a nearly fifty-fifty will save.

[DracoDei]

Probably true... even with the half damage on the made save...

[Icewalker]

That was actually one reason I chose it: 1d8+2 could knock out a first level character. However with a will save, they would be more likely to make it.

Fluffwise it doesn't really work with a slam attack because, well, it doesn't have arms. It can't really be taken and used either, due to the circumstances, so I'm not worried about that one.

I'll drop the HD to 1, which also makes the ILW 1d8+1, not +2.
Also lowering NA by 2 and DR to 1.
Has to be Medium for fluff reasons, but now with hp of 25, AC 13, and DR 1, would it still wreck a first level party?

[Azerian Kelimon]

If this thing has immunity to magic, I'd reduce it's HP's to 14. Else, I'd keep it as is. With such high HP's, if it's magic immuned, it's going to TPK people, particularly with that DR. Now, if a caster can do something to it, things change dramatically.

[Icewalker]

Hmm. Storywise I don't really want it to be immune to magic. So no, no magic immunity.

[Jaerc]

Without delving into the realm of advice-giving and instead just straight analyzing this guy. A midrange CR 2.