Grimlocks are clearly inspired by the Morlocks from H. G. Well's novel the Time Machine (and the 1960 Hollywood adaptation). Albie Fiore first statted them out in the original Fiend Folio and they have been a staple D&D monster ever since.
The following text is Open Game Content.

Monstrous Humanoid
Grimlocks are a race of savage, degenerate creatures dwelling deep underground in scattered tribes. Although Grimlocks are blind, they have excellent senses that allow them to survive in the lightless realms.
The grimlock's class skills are Climb (Str), Hide (Dex), Listen (Wis), and Spot (Wis).
All of the following are class features of the Grimlock monster class.
Weapons and Armor Proficiency: Grimlocks are automatically proficient with all simple weapons and the battleaxe.
Feats: A grimlock receives one feat at 1st level. After 4th level it gains feats normally according to its character level.
Blindsight (Ex): Grimlocks can sense all foes within range as a sighted creature would. Beyond that range, they treat all targets as having total concealment. Grimlocks are susceptible to sound- and scent-based attacks, however, and are affected normally by loud noises and sonic spells (such as ghost sound or silence) and overpowering odors (such as stinking cloud or incense-heavy air). Negating a grimlock's sense of smell or hearing reduces this ability to normal Blind-Fight (as the feat). If both these senses are negated, a grimlock is effectively blinded.
Natural Camouflage (Ex): A grimlock's dull gray skin helps it hide in its native terrain, conferring a racial bonus on Hide checks when in mountains or underground.
Scent (Ex): Beginning at 2nd level, a grimlock can detect approaching enemies, sniff out hidden foes, and track by sense of smell within the given range (double range if the scent is upwind, one-half-range if the scent is downwind). When the grimlock detects a scent, the exact location of the source is not revealed -- only its presence somewhere within range. The grimlock can take a move action to note the direction of the scent. Whenever the grimlock comes within 5 feet of the source, the grimlock pinpoints the source's location.
| Level | Hit Dice | Base Attack Bonus | Fort Save | Ref Save | Will Save | Skill Points | CR | Special |
|---|---|---|---|---|---|---|---|---|
| 1st | 1d8 | +1 | +0 | +2 | +2 | (2 + Int mod) x 4 | 1/2 | Feat, +1 natural armor, blindsight 10 ft., natural camouflage +4 |
| 2nd | 1d8 | +1 | +0 | +2 | +2 | - | 1/2 | +2 Con, +2 natural armor, blindsight 20 ft., natural camouflage +6, scent 10 ft. |
| 3rd | 2d8 | +2 | +0 | +3 | +3 | 2 + Int mod | 1 | +2 Dex, +3 natural armor, blindsight 30 ft., natural camouflage +8, scent 20 ft. |
| 4th | 2d8 | +2 | +0 | +3 | +3 | - | 1 | +2 Str, +4 natural armor, blindsight 40 ft., natural camouflage +10, scent 30 ft. |