Leather is basically the skin of animals - however, only certain animals will provide you with this crafting material in Creativerse.
This material can only be seen ingame as an icon resembling a brown unrolled hide, not as a 3D item.
How to obtain
Leather can be obtained from many Creatures - most often from yellow daylight Pigsies, Night Pigsies and Night Hoglets, also from Reinbeaus, somewhat more rarely from green daylight Leafies and Night Leafies, but also rarely from BossHogs in Savannahs, and only very rarely from Night Twiggies.
Leather can be collected either by killing these Creatures and looting their Loot Bags, or by taming these Creatures, feeding them their exact favorite type of Food and then harvesting from them by "pulling" them with the ArcTek Gauntlet (with or without Mining Cells equipped).
Please note that Creatures will always only "drop" their best possible pet-harvest after being fed their exact favorite Food as shown in their pet windows. Pet-harvests will then consist of up to 3 times the amount of items than you could loot from them after killing them (or dismissing them when they are your pets).
How to use
Leather is a necessary crafting ingredient for Leather Armor (Leather Breastplates, Leather Leggings, Leather Armguards and Leather Pauldrons), Obsidian Armor (Obsidian Breastplates, Obsidian Leggings, Obsidian Armguards and Obsidian Pauldron), Vlad-a-Rangs, Haunted Fireworks, Placemats, Blocky the Snowman, Industrial Switches, Industrial Levers, Industrial Bellows, Holiday Music Boxes, Candy Skull Banners, Picture Frames, Customazing Curtains, Galactic Captain's Chairs, Cherishizing Chairs, Cushceptional Couches, Curvaciously Cushceptional Couches, Ostenduring Ottomans, Medieval Tables, Medieval Banner Walls, Medieval Carpeted Stairs, Holiday Garlands, Holiday Wreaths, Jaunstounding Jabots and for the Industrial Crowbar.
Like most animal materials, this crafting-material cannot be put into your quickbar and cannot be placed into the world.
It also cannot be displayed on/in display containers like Stone Wall Shelves, Placemats, Wood Planters, Flower Pots, Galactic Grav-Chambers, Hidden Temple Altars, Frozen Containers, Snow Buried Containers, Holiday Mantles, Holiday Decorative Trees, Cabernatious Cabinets or the like.