The Hashalaq Quori is an aberration that looks very different from the humanoids that typically get access to disguise self. It is unclear to me what forms are available to them when they use this spell.
The key restriction from the spell is:
You can’t change your body type, so you must adopt a form that has the same basic arrangement of limbs.
But the hashalaqs have no “basic arrangement of limbs”:
In their natural form, hashalaqs are composed of hundreds of translucent tendrils. They can compress and configure these tendrils to form a wide range of simple shapes.
As well, the creatures don’t have the line of text that allows the lamia, for example, to use humanoid forms.
How, then, should ability be interpreted? Can the hashalaq reconfigure its natural form to be humanoid in shape, allowing it to take the form of a humanoid with disguise self? Can it only transform into a different-looking amorphous creature? Or is there a different interpretation that works better here?