Torches are items that are equipped in the "Torch" slot, that the player can pick up to increase light radius, which is 2 tiles long by default.
The light that torches emit also passes through walls, allowing you to see the enemy early and find hidden rooms easier.
The player can only equip one torch at a time; picking up a new torch drops their current one.
Note that enemies are easier alerted the bigger your light radius is.

Torch Light Radius Notes
Tool torch
Torch 2
Bright Torch
Torch 3
Luminous Torch
Torch obsidian
Obsidian Torch
+2/3/4 Increases light radius depending on the current Groove Chain multiplier.
Torch glass
Glass Torch
+4 Allows the player to see all monsters and NPCs, even when out of sight. Does not alert enemies of the player's presence out of their light radius. Breaks if the player takes damage.
Torch infernal
Infernal Torch
+2 Upon digging up a wall torch (or "wall mushroom" in Zone 2), the player casts an "Infernal Fire!" spell, identical to Greater Spell fireballFireball (deals 8 normal damage).

Digging a wall with the PickaxePickaxe casts the spell each hit.

Torch foresight
Torch of Foresight
+2 Makes traps visible across the entire level while equipped, even when out of sight.
Torch of Walls Amplified dlc
+2 Reveals all walls in the dungeon, but not floors.
Torch of Strength Amplified dlc
+2 Increases attack damage by 1.