Help coming up with a huge CR 3-4 aberration similiar to an anglerfish.

[Redchigh]

The idea, is a huge but slow blind and deaf aberration that lures in its prey.

Perhaps a hallucinatory aura that helps prey fall for its trap?

The idea is the party (if they fail perception a few times) will see something- Perhaps a sobbing child, or a small boulder with a man giving away drinks of potions of CLW, or something similiar. If enough saves are failed and they reach out to the child/cup of CLW/whatever, they stick to whatever they touch (the creature's adhesive tongue) and hear a deafening roar as the ground shakes, and massive teeth rise out of the ground and clamp around them.

If they think fast, I'll make sure they survive, but it serves to introduce them to the campaign. (They are all level 1, but there are 8 of them.)

Can someone help me with an applicable stat block?

Originally the creature was disguised as a building or cave, with the 'tongue' in the opening, but I wasn't sure it was 'realistic' enough.

The campaign is lovecraftian horror and full of aberrations, undead, and occasionally reanimated dead aberrations, so unpredictably deadly things are common (Players will be reminded, running is always an option.)

[Kyras Ausks]

have you heard oh my buddy Stumpy
really though a small amount of dm flavor and thats pretty much what you are looking for

[+5 Toaster]

This makes me think of banjo tooie.

[Redchigh]

Interestingly similiar... Any advice on simultaniously increasing its size and shrinking its CR?

I suppose removing the tentacles and reach, reducing AC and hp, and giving it swallow whole with an adhesive tongue would work..

[Kyras Ausks]

young template possibly x2 fake the size but if your group is high on magic and or range its dc could count for much less

[Quath]

I would say reflavor and resize a Giant Frog. Give it the Wolf-in-sheep's-clothing reanimation ability and some kind of ability to perfectly recreate any sound it's heard before. It will already have the sticky tongue and swallow whole that way and it's always easier to increase CR than it is to lower it.

[MrSin]

Aboleth happen to be an ancient lovecraftian psychic monstrosity. They have a psionic version in 3.5 even. You might consider using it as a base and changing it a little, or at least including it later in the campaign.