diff --git a/lua/biome.lua b/lua/biome.lua
new file mode 100644
index 0000000..0373b30
--- /dev/null
+++ b/lua/biome.lua
@@ -0,0 +1,88 @@
+-- This file takes care of cave biomes
+
+noordstar_caves.registered_biomes = {}
+
+-- Clean the input and return a valid shape def
+-- If the input is invalid, return nil
+local function clean_def(def)
+    if type(def.name) ~= "string" then
+        return nil
+    end
+    if type(def.heat_point) ~= "number" then
+        return nil
+    end
+    if type(def.humidity_point) ~= "number" then
+        return nil
+    end
+
+    local d = {
+        name = def.name,
+        heat_point = def.heat_point,
+        humidity_point = def.humidity_point,
+    }
+
+    -- Position
+    if type(def.min_pos) == "table" then
+        d.minp = {
+            x = def.min_pos.x or -1e5,
+            y = def.min_pos.y or -1e5,
+            z = def.min_pos.z or -1e5,
+        }
+    elseif type(def.y_min) == "number" then
+        d.minp = { x = -1e5, y = def.y_min, z = -1e5 }
+    else
+        d.minp = { x = -1e5, y = -1e5, z = -1e5 }
+    end
+
+    if type(def.max_pos) == "table" then
+        d.maxp = {
+            x = def.max_pos.x or 1e5,
+            y = def.max_pos.y or 1e5,
+            z = def.max_pos.z or 1e5,
+        }
+    elseif type(def.y_max) == "number" then
+        d.maxp = { x = 1e5, y = def.y_max, z = 1e5 }
+    else
+        d.maxp = { x = 1e5, y = 1e5, z = 1e5 }
+    end
+
+    -- Optional nodes
+    if type(def.node_dust) == "string" then
+        d.node_dust = def.node_dust
+    end
+    if type(def.node_floor) == "string" then
+        d.node_floor = def.node_floor
+    end
+    if type(def.node_wall) == "string" then
+        d.node_wall = def.node_wall
+    end
+    if type(def.node_roof) == "string" then
+        d.node_roof = def.node_roof
+    end
+    if type(def.node_shell) == "string" then
+        d.node_shell = def.node_shell
+    end
+    if type(def.depth_shell) == "number" then
+        d.depth_shell = def.depth_shell
+    else
+        d.depth_shell = 0
+    end
+
+    return d
+end
+
+function noordstar_caves.register_biome(def)
+    local d = clean_def(def)
+
+    if d ~= nil then
+        noordstar_caves.registered_biomes[d.name] = d
+    end
+end
+
+function noordstar_caves.unregister_biome(name)
+    noordstar_caves.registered_biomes[name] = nil
+end
+
+function noordstar_caves.clear_registered_biomes()
+    noordstar_caves.registered_biomes = {}
+end