Determing CR on my Homebrew; Help

[Edwin]

Hello.

Recently, I've been toying with the idea of trying dm'ing myself, for, as of yet, I have only been a player.
To that effect, I decided I'd homebrew a monster, one that I could employ in my campaign.

Sadly, I have always had trouble with determing the CR of stuff.
So, now I ask of you, please, help me with the CR on my mooks:

Sorcerous Slime, lesser.

Spoiler

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Sorcerous Slime, lesser
Chaotic Evil Small Abberation
Hit Dice: 20 hp (3d8+6)
Initiative: 1+
Speed: 30 ft.
Armor Class: 14 (+2 Natural armor, +1 dex, +1 Small size) 11 touch, 14 flat-footed
Base Attack/Grapple: +2/+0
Attack: Tentacle +5 (1d3+2)
Full Attack: 2 Tentacle +5 (1d3+2)
Space/Reach: 5 ft./5 ft.
Saves: Fort +2, Ref +1, Will +3
Abilities: Str 15, Dex 13, Con 14, Int 21, Wis 10, Cha 12
Skills: Listen +6, Spot +6, Concentration +3, Knowledge: Arcana +3, Knowledge: The Planes +3, Spellcraft +3,
Survival +3, Hide +4(Small size)
Feats: Combat Casting
Equipment: None

Improved Grapple: This creature gains Improved Grapple as a bonus feat.
Spell-like Abilities: 2/day; Acid Splash 1/day; Comprehend Languages

Sorcerous Slimes speak common, and can communicate with other Sorcecous Slimes telepathically in a range of 30ft.

Sorcerous Slimes are vaguely humanoid, black creatures, made primarily of slime, with no arms. Instead, they have two tentacles sprouting from their backs. They don't have a head, or any vital organs, except for a brain, which is located in the stomach. They are roughly the size of an average human. They are also highly intelligent creatures, who usually employ other, dumber creatures to do their work.

Combat: Sorcerous slimes prefer to stay in the back, commanding other creature to do the melee fighting, while they use their Acid Splash to weaken their foes, and then swoop in to flank an enemy, and then finish them off with a full attack.

And the normal version: Sorcerous Slime.

Spoiler

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Sorcerous Slime
Chaotic Evil Medium Abberation
Hit Dice: 45 (6d8+18)
Initiative: 0+
Speed: 30 ft.
Armor Class: 12 (+2 Natural Armor) 10 touch, 12 flat-footed
Base Attack/Grapple: +4/+8
Attack: Tentacle +8 (1d4+4)
Full Attack: 2 Tentacle +8 (1d4+4)
Space/Reach: 5 ft./5 ft.
Saves: Fort +5, Ref +2, Will +6
Abilities: Str 19, Dex 11, Con 16, Int 21, Wis 12, Cha 14
Skills: Listen +9, Spot +9, Concentration +4, Knowledge: Arcana +4, Knowledge: The Planes +4, Spellcraft +4,
Survival +4
Feats: Combat Casting, Power Attack
Equipment: None
Improved Grapple: This creature gains Improved Grapple as a bonus feat.
Spell-like Abilities: 3/day; Acid Splash, Resistance 2/day; Magic Missile 1/day; Comprehend Languages, Expeditious Retreat, Burning Hands

Sorcerous Slimes speak common, and can communicate with other Sorcecous Slimes telepathically in a range of 30ft.

Sorcerous Slimes are vaguely humanoid, black creatures, made primarily of slime, with no arms. Instead, they have two tentacles sprouting from their backs. They don't have a head, or any vital organs, except for a brain, which is located in the stomach. They are roughly the size of an average human. They are also highly intelligent creatures, who usually employ other, dumber creatures to do their work.

Combat: Sorcerous slimes prefer to stay in the back, commanding other creature to do the melee fighting, while they use their Spell-like abilities to pick on their foes, and then swoop in to flank an enemy, applying Power Attack to finish them off with a full attack.

If you see something very wrong about the creatures, please tell me, too.

Also, if I were to mush the lesser version in with two gnolls, would I just add up their respective CR to determine the actual CR? Or how would I go about doing that?

Thanks in advance!

[afroakuma]

Try The Vorpal Tribble's method:

1. Divide its average HP by 4.5 to 6,
4.5 for 5 HD or lower, 5 for 6-10 HD, 5.5 for 11-15 HD, 6 for 16-20 HD.
2. Add 1 for each five points above 10 its AC is, minusing 1 for every 5 below.
3. Add 1 for each special attack (+2 to +5 or more if its got a decent number of spells in its spell-like abilities).
4. Add 1 for each quality unless you deem it worthy of more. Add 1 for each resistance and 10 points of DR it has, and 2 for each immunity.
5. Add 1 for every two bonus feats it has.
6. Divide by 3.

[Edwin]

Try The Vorpal Tribble's method:

1. Divide its average HP by 4.5 to 6,
4.5 for 5 HD or lower, 5 for 6-10 HD, 5.5 for 11-15 HD, 6 for 16-20 HD.
2. Add 1 for each five points above 10 its AC is, minusing 1 for every 5 below.
3. Add 1 for each special attack (+2 to +5 or more if its got a decent number of spells in its spell-like abilities).
4. Add 1 for each quality unless you deem it worthy of more. Add 1 for each resistance and 10 points of DR it has, and 2 for each immunity.
5. Add 1 for every two bonus feats it has.
6. Divide by 3.

Thanks!

How about the multiple monsters question? Do you simple add up the CR?

[Magnor Criol]

For determining the CR of an encounter with multiple monsters, use a handy-dandy encounter calculator like this one. There's a number of them out there, that's just one of the lot.

-E- Oh, I see what your question is, I think.

You always price monsters individually, so their CR will be whatever you deem it suited to, regardless of whether or not it's supposed to be encountered with other things. A CR rates that creature only.

Then you'll add that creature's CR in with the CRs for whatever other creatures come as part-and-parcel with it, using a calculator like above, for each encounter.