Martin Hamilton is giving away a pack of simple substances, which can help you make some gory monsters.
You can’t beat free. The provided materials are made with 4k tile-able maps. The artist used Algorithmic’s bitmap2material program to make the textures from photographs. All materials contain Ambient Occlusion, Base Color, Height, Normal, and Roughness maps.
You can download the materials here. https://gum.co/yZycf