Super Metroid's four guardians.

[Valigarmander]

We know Ridley is a high-ranking and intelligent space pirate. What about Kraid, Phantoon and Draygon? Are they high-ranking pirates too? This seems to be the implication, but it's never really clarified. They could just be mindless beasts employed by Mother Brain to protect the path to Tourian. What are your thoughts about this?

[I REALLY HATE POKEMON!]

Wait, Ridley is intelligent? And has a rank? What is he, part of a monster militia? I've never beaten a Metroid so this is a surprise to me. How interesting.

[Marilink]

^Yeah man, Ridley is fully sentient and intelligent.

[Random User]

I would assume Kraid is a Space Pirate as well. It's stated that Phantoon "taps into the brainwaves of Mother Brain" from the Wrecked Ship in the instruction booklet. It could be haunting the Wrecked Ship just for that. As far as Draygon goes I'm not really sure.

[ScottyMcGee]

Metroid wiki says Kraid is a high-ranking Space Pirate too.

"The Metroid Prime manual describes Ridley and Kraid as the Space Pirate army's "mainstays"; one could easily imagine this colossus as the muscle and backbone behind Pirate attacks or raids."

[е и ժ е я]

Not directly related, but it's originally implied that SM's Kraid is not normally super-huge but has been grown via the same kind of radiation used on the metroid hatchling, but they've gotten a bit muddled on that since. The gigantic sidehoppers are also an example of this. They haven't refrained from experimenting on and modifying Ridley as well, so it holds that they wouldn't hesitate to do so with Kraid.

It's interesting that the Space Pirates seem to value power over species, as Ridley and Kraid are highly ranked.

I don't think Kraid is necessarily sentient so much as just a juggernaut they favor. The Phantoon itself is probably just incidentally held in sway by the corrupted Mother Brain that the Pirates employ.