Kraid (also Kraid's Lair) is an area in Brinstar.
In the original Metroid, Kraid's Lair (also known as Mini-Boss Hideout I) consists of a tall grey chamber, with several doors on each side. Many of these lead to long purple corridors. Common enemies found in this area are Rippers, Skrees, Side Hoppers, Zeelas, Memus and Geegas. Acid is commonly found throughout this area like in other rooms of Brinstar. In order to reach this area, Samus must have the Morph Ball and bombs.
Metroid: Zero Mission
In Metroid: Zero Mission, there are a few changes. There are power handholds throughout the area that have to be activated to cross large gaps. The Mua also appears as a mini-boss. In order to get to Kraid himself though, Samus must obtain one of the Unknown Items to be able to destroy certain blocks. Additionally, the Speed Booster can be obtained by defeating Kraid.
While there isn't a Kraid's Lair by title, there is a designated area for him within Brinstar. His hideout is located east, to the right of the elevator leading to Norfair. His entrance has the same beastly decor that is in the original Metroid. Kraid's hideout requires Super Missiles, and the High-Jump Boots. It is possible to gain access without the High-Jump Boots by using the Bomb Jump or Wall Jump techniques, but first-time players are unlikely to use these methods.
Kraid's area has a mechanical look here, with bolts and panels scattered on the walls. When getting closer to Kraid, the music changes to signify an upcoming boss fight, and the walls are green. There are even curved spikes on the ceiling similar to the original Metroid, and a Mini Kraid. Samus can also obtain the Varia Suit upon defeating Kraid.