diff --git a/app/models/collection_weapon.rb b/app/models/collection_weapon.rb
index 7399ed0..a9288cb 100644
--- a/app/models/collection_weapon.rb
+++ b/app/models/collection_weapon.rb
@@ -15,6 +15,7 @@ class CollectionWeapon < ApplicationRecord
   has_many :grid_weapons, dependent: :nullify
 
   before_destroy :orphan_grid_items
+  before_validation :set_default_exorcism_level, on: :create
 
   # Set defaults before validation so database defaults don't cause validation failures
   attribute :awakening_level, :integer, default: 1
@@ -174,4 +175,16 @@ class CollectionWeapon < ApplicationRecord
   def orphan_grid_items
     grid_weapons.update_all(orphaned: true, collection_weapon_id: nil)
   end
+
+  ##
+  # Sets default exorcism_level to 1 for befoulment weapons if not provided.
+  #
+  # @return [void]
+  def set_default_exorcism_level
+    return unless weapon.present?
+    return unless exorcism_level.nil?
+    return unless weapon.weapon_series&.augment_type == 'befoulment'
+
+    self.exorcism_level = 1
+  end
 end
\ No newline at end of file
diff --git a/app/models/grid_weapon.rb b/app/models/grid_weapon.rb
index b01b824..0dc9bac 100644
--- a/app/models/grid_weapon.rb
+++ b/app/models/grid_weapon.rb
@@ -56,6 +56,7 @@ class GridWeapon < ApplicationRecord
   validate :no_conflicts, on: :create
 
   before_save :assign_mainhand
+  before_validation :set_default_exorcism_level, on: :create
 
   ##### Amoeba configuration
   amoeba do
@@ -245,4 +246,16 @@ class GridWeapon < ApplicationRecord
   def assign_mainhand
     self.mainhand = (position == -1)
   end
+
+  ##
+  # Sets default exorcism_level to 1 for befoulment weapons if not provided.
+  #
+  # @return [void]
+  def set_default_exorcism_level
+    return unless weapon.present?
+    return unless exorcism_level.nil?
+    return unless weapon.weapon_series&.augment_type == 'befoulment'
+
+    self.exorcism_level = 1
+  end
 end
diff --git a/db/data/20260104000002_populate_max_exorcism_level.rb b/db/data/20260104000002_populate_max_exorcism_level.rb
new file mode 100644
index 0000000..dc3e0b4
--- /dev/null
+++ b/db/data/20260104000002_populate_max_exorcism_level.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class PopulateMaxExorcismLevel < ActiveRecord::Migration[8.0]
+  def up
+    # Set max_exorcism_level = 5 for all weapons that belong to a series with befoulment augment type
+    updated = Weapon
+      .joins(:weapon_series)
+      .where(weapon_series: { augment_type: :befoulment })
+      .update_all(max_exorcism_level: 5)
+
+    puts "  Updated #{updated} weapons with max_exorcism_level = 5"
+  end
+
+  def down
+    Weapon
+      .joins(:weapon_series)
+      .where(weapon_series: { augment_type: :befoulment })
+      .update_all(max_exorcism_level: nil)
+  end
+end
diff --git a/spec/requests/collection_weapons_controller_spec.rb b/spec/requests/collection_weapons_controller_spec.rb
index 310cb80..ef93f93 100644
--- a/spec/requests/collection_weapons_controller_spec.rb
+++ b/spec/requests/collection_weapons_controller_spec.rb
@@ -279,4 +279,63 @@ RSpec.describe 'Collection Weapons API', type: :request do
       expect(response).to have_http_status(:not_found)
     end
   end
+
+  describe 'default exorcism_level for befoulment weapons' do
+    let(:odiant_series) { create(:weapon_series, :odiant) }
+    let(:befoulment_weapon) { create(:weapon, weapon_series: odiant_series, max_exorcism_level: 5) }
+    let(:regular_weapon) { create(:weapon) }
+
+    it 'sets exorcism_level to 1 when creating with befoulment weapon and no exorcism_level provided' do
+      attributes = {
+        collection_weapon: {
+          weapon_id: befoulment_weapon.id,
+          uncap_level: 3,
+          transcendence_step: 0
+        }
+      }
+
+      post '/api/v1/collection/weapons', params: attributes.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['exorcismLevel']).to eq(1)
+    end
+
+    it 'respects provided exorcism_level for befoulment weapon' do
+      befoulment_modifier = create(:weapon_stat_modifier, :befoulment)
+
+      attributes = {
+        collection_weapon: {
+          weapon_id: befoulment_weapon.id,
+          uncap_level: 3,
+          transcendence_step: 0,
+          exorcism_level: 3,
+          befoulment_modifier_id: befoulment_modifier.id,
+          befoulment_strength: 5.0
+        }
+      }
+
+      post '/api/v1/collection/weapons', params: attributes.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['exorcismLevel']).to eq(3)
+    end
+
+    it 'does not set exorcism_level for non-befoulment weapons' do
+      attributes = {
+        collection_weapon: {
+          weapon_id: regular_weapon.id,
+          uncap_level: 3,
+          transcendence_step: 0
+        }
+      }
+
+      post '/api/v1/collection/weapons', params: attributes.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['exorcismLevel']).to be_nil
+    end
+  end
 end
\ No newline at end of file
diff --git a/spec/requests/grid_weapons_controller_spec.rb b/spec/requests/grid_weapons_controller_spec.rb
index f1963f8..c5a4d95 100644
--- a/spec/requests/grid_weapons_controller_spec.rb
+++ b/spec/requests/grid_weapons_controller_spec.rb
@@ -345,6 +345,71 @@ RSpec.describe 'GridWeapons API', type: :request do
     end
   end
 
+  describe 'default exorcism_level for befoulment weapons' do
+    let(:odiant_series) { create(:weapon_series, :odiant) }
+    let(:befoulment_weapon) { create(:weapon, weapon_series: odiant_series, max_exorcism_level: 5) }
+    let(:regular_weapon) { create(:weapon) }
+
+    it 'sets exorcism_level to 1 when creating with befoulment weapon and no exorcism_level provided' do
+      params = {
+        weapon: {
+          party_id: party.id,
+          weapon_id: befoulment_weapon.id,
+          position: 1,
+          uncap_level: 3,
+          transcendence_step: 0
+        }
+      }
+
+      post '/api/v1/grid_weapons', params: params.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['grid_weapon']['exorcismLevel']).to eq(1)
+    end
+
+    it 'respects provided exorcism_level for befoulment weapon' do
+      befoulment_modifier = create(:weapon_stat_modifier, :befoulment)
+
+      params = {
+        weapon: {
+          party_id: party.id,
+          weapon_id: befoulment_weapon.id,
+          position: 1,
+          uncap_level: 3,
+          transcendence_step: 0,
+          exorcism_level: 4,
+          befoulment_modifier_id: befoulment_modifier.id,
+          befoulment_strength: 5.0
+        }
+      }
+
+      post '/api/v1/grid_weapons', params: params.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['grid_weapon']['exorcismLevel']).to eq(4)
+    end
+
+    it 'does not set exorcism_level for non-befoulment weapons' do
+      params = {
+        weapon: {
+          party_id: party.id,
+          weapon_id: regular_weapon.id,
+          position: 1,
+          uncap_level: 3,
+          transcendence_step: 0
+        }
+      }
+
+      post '/api/v1/grid_weapons', params: params.to_json, headers: headers
+
+      expect(response).to have_http_status(:created)
+      json = JSON.parse(response.body)
+      expect(json['grid_weapon']['exorcismLevel']).to be_nil
+    end
+  end
+
   # Debug hook: if any example fails and a response exists, print the error message.
   after(:each) do |example|
     if example.exception && defined?(response) && response.present?