The Rotten is built up of what must be dozens of bodies chained and melted together. They move due to various arms and legs crawling in tandem, their hands are made from the legs and arms of people, causing the digits to be very long and unnerving. They don a cage helm and wield a large butcher's knife, both rusted and bent. Terrifying presence. 10/10 Spookiness.

The Rotten, despite their large size and horrifying design, are not all that powerful. While they do possess physical strength, they move rather slowly, aren't extremely coordinated, and can have their limbs dismembered. Their magic abilities are also quite limited, only having a small AOE blast. 6/10.

Transform is going to be a 6. They are composed of normal humans, however in a very patchwork way, with limbs sewn all over and broken and bent in horrible ways.

The name feels wrong to me. The Rotten is pretty on-brand for an undead character, however, this character is pretty bereft of rot. And the theme isn't really rotting, it's sewing, it's combining. it's growing. 4/10 for The Rotten.