Forge is a Fire-affinity component. It is under the Offense tree.
Effect
Smelts the target block. Does not give XP from smelting. The target block will stay in place if the molten recipent also is a block (for example sand to glass) and the item dropped will spawn somewhere in your hit box letting you pick it up without having to go to the block you melt.
Requirements
All the following items must be unlocked to be able to unlock Forge.
Trivia
Forge is under the Offense tree, rather than the utility tree. This is not a glitch
Forge can be used for instant mining spells as it can give the player bars of metal instantly without the need for a furnace.
This component bypasses most plugins that prevent breaking/interacting with blocks in certain areas, such as worldguard, townie and factions.