Jewel beasts and the Lord of Jewels are monsters associated with the Jumi Race.
Jewel Beasts are crystal like monsters which Sandra the Jewel Thief uses on you many times. They have a spider like base with something similar to a scorpion tail with a mouth on the end of it growing out of them. Their neck contains a human head and torso suggesting they could be some sort of twisted Jumi. The fact that Sandra can summon them with some sort of jewels goes to back this theory up. Their main attacks are flailing with their head and biting you. They can all shoot blasts of energy out of their mouths. Some of them have the ability to stand on their mouth and drill at you with their feet, and sometimes they will even kick up multiple rocks while drilling.
Lord of Jewels 999 and Lord of Jewels 1000
The Lord of Jewels is a mysterious fishy looking character first met in Mekiv Caverns. He seems to have some relation to Jumis as he can eat their cores and combine them together. With 1000 cores he can successfully ressurect a Jumi. After obtaining 999 cores (core 999 is either Elazul or Pearl depending on your choices) he will transform into a large fishy creature clutching a giant jewel. In the Lord of Jewels 999 form it attacks by whipping its tail and smashing you across the room. It has multiple laser special abilities as well as crystal ones. Jeweled Beam sends out a group of crystals which shoot lasers at one another, Search Beam searches you out and then blasts you, and Crystal Shards creates many giant stalagmites out of crystals scattered on the ground. After this form is defeated Sandra sacrifices herself to the Lord of Jewels and he becomes a giant whale monster. Lord of Jewels 1000 fights with laser blasts and a Cosmic Gem ability which sends exploding crystals down on the battlefield.