Skillcloaks adds new items to assist you with different types of tasks in the form of Cloaks you can equip in a Curio back slot. You need Curios API (Forge) to play this mod. Caelus API (Forge) and Lucent provide additional features but aren't required. The Cloaks come in different types of sacks by default which are obtained by trading with villagers. This mod has many config options to help modpack makers tweak whichever aspect they want.
The Sacks are sold by Master tier Villagers
The Brown Sack is sold by the Fletcher and the Toolsmith
The Green Sack is sold by the Farmer and the Fisherman
The Red Sack is sold by the Armorer and the Weaponsmith
The Blue Sack is sold by the Librarian and the Cleric
The Black Sack is given to you when you Right-click a Nitwit villager with a stack of emeralds in your hand
Specific Cloaks come from specific colored Sacks
Agility Cloak: You become exhausted much slower, which means you need less food. Comes from the Blue Sack
Attack Cloak: Your armor has a chance to not lose durability. Comes from the Red Sack
Construction Cloak: Pressing the cloak ability key teleports you where you last set your spawnpoint. Comes from the Blue Sack
Cooking Cloak: Right-clicking cooks the food in your hand if you're holding a Flint and Steel in your other hand. Comes from the Brown Sack
Crafting Cloak: Pressing the cloak ability key opens a 3x3 crafting menu. Comes from the Brown Sack
Defence Cloak: Prevents your death similarly to the Totem of undying, but has a cooldown of one full Minecraft day. Comes from the Red Sack
Farming Cloak: Using bonemeal affects a larger area. Comes from the Green Sack
Firemaking Cloak: You can place down sticks and they will turn into torches. If Lucent is installed, also provides a light source that follows you. Comes from the Blue Sack
Fishing Cloak: Your luck is increased while fishing. Comes from the Green Sack
Fletching Cloak: Loading an arrow into a crossbow has a chance to give you a copy of the arrow. Comes from the Brown Sack
Herblore Cloak: You can make potions with right-click while holding the ingredients in your hands. Comes from the Brown Sack
Hitpoints Cloak: All healing on the wearer is doubled. Comes from the Red Sack
Hunter Cloak: Killing an enemy pulls its drops and xp to you. Comes from the Green Sack
Magic Cloak: You can transfer enchantments and curses from items into books by holding them in your hands and right-clicking. Comes from the Red Sack
Mining Cloak: You have fortune while mining. Comes from the Green Sack
Prayer Cloak: You don't lose any xp or the Cloak on death. Comes from the Red Sack
Ranging Cloak: Shooting an arrow with a bow has a chance to give you a copy of the arrow. Comes from the Red Sack
Runecraft Cloak: Your tools have a chance to not lose durability. Comes from the Brown Sack
Slayer Cloak: Your attacks execute low health monsters. Comes from the Blue Sack
Smithing Cloak: Right-clicking smelts the ores in your hand if you're holding a Flint and Steel in your other hand. Comes from the Brown Sack
Strength Cloak: Gives you knockback immunity. Comes from the Red Sack
Thieving Cloak: Enemies need to be closer to see you. Comes from the Blue Sack
Woodcutting Cloak: You can cut down an entire tree by destroying one block from it. Comes from the Green Sack
Max Cloak: Has the effects of ALL the other Skillcloaks. You can crouch and press the ability key to change it's mode (switch what the ability button does when wearing the Cloak). Comes from the Black Sack