A ebi-kreen resembled a giant crayfish, bipedal and standing 4.5–7 feet (1.4–2.1 meters) high and weighing 100–375 pounds (45–170 kilograms); a full-grown adult averaged at 6 feet (1.8 meters) and 200 pounds (90 kilograms). They had exoskeletons over their entire bodies. They had six limbs protruding from their thorax: two for walking, two ending in large pincers and two as arms, ending in four-fingered claw-like hands capable of tool- and weapon-use. Their insectoid heads had two yellow, multi-faceted compound eyes; two small antennae sprouting from the top; and a complex jaw structure with large sharp mandibles. It was extremely difficult to distinguish the males and females.
The carapace of a ebi-kreen was typically a deep red in hue, but could vary from a dark brown to a bright blue color, as best suited the environment. This enabled ebi-kreen to blend in with the rocky sea bottom they dwelled in.
Ebi-kreen wore little to no clothing or armor. Instead, they wore only simple belts, harnesses, or slings to hold their food, equipment, and weaponry, and only as much as they needed. They did not make or wear any kind of adornments.
Ebi-kreen had superior physical abilities compared to a human, with high strength and great agility. They were faster on their feet, and had an incredibly quick swim speed, if only in short bursts. They were quick enough to deflect or dodge an incoming projectile. Their carapace was naturally armored, being tough and resistant to impact, and its red color helped them hide in the dark sea bottom, where low light and darkvision make them all but invisible. Ebi-kreen typically grew to be skilled in their senses, hiding, jumping, climbing, and balancing.
A ebi-kreen's four claws and a bite from its mandibles were dangerous natural weapons. They secreted a paralyzing poison from their mouths, sufficient for a single venomous bite per day. This could hamper a victim's agility, or cause paralysis for several minutes.
Ebi-kreen were naturally psionic beings, possessing psionic energy and knowing innately a number of powers. A ebi-kreen could manifest several powers natually and often became skilled hunters through psionic manipulation of their prey.
They could see in the dark through darkvision, and did not sleep at all, making them immune to sleep spells and the like.
Unlike the similar thri-kreen of the land, ebi-kreen were exceptionally long lived, sometimes living for centuries.
It is not known if ebi-kreen had definable personalities as humans would know them. No emotions could be discerned from their insectoid faces or their patterns of behavior, though rapid twitching of their antennae or mandibles indicated agitation. Predictably, it was very difficult for ebi-kreen to deal with others, and they were hard to negotiate with. They neither avoided nor sought out other races, but merely existed alongside them, sharing territory without conflict.