diff --git a/app/models/grid_character.rb b/app/models/grid_character.rb
index e60bcf9..ac8faea 100644
--- a/app/models/grid_character.rb
+++ b/app/models/grid_character.rb
@@ -5,40 +5,60 @@ class GridCharacter < ApplicationRecord
 
   validate :awakening_level, on: :update
   validate :transcendence, on: :update
-  validate :over_mastery_attack, on: :update
-  validate :over_mastery_hp, on: :update
+  validate :validate_over_mastery_values, on: :update
+  validate :validate_aetherial_mastery_value, on: :update
   validate :over_mastery_attack_matches_hp, on: :update
 
   def awakening_level
-    unless awakening.nil?
-      errors.add(:awakening, 'awakening level too low') if awakening["level"] < 1
-      errors.add(:awakening, 'awakening level too high') if awakening["level"] > 9
-    end
+    return if awakening.nil?
+
+    errors.add(:awakening, 'awakening level too low') if awakening['level'] < 1
+    errors.add(:awakening, 'awakening level too high') if awakening['level'] > 9
   end
 
   def transcendence
-    errors.add(:transcendence_step, 'character has no transcendence') if transcendence_step > 0 && !character.ulb
+    errors.add(:transcendence_step, 'character has no transcendence') if transcendence_step.positive? && !character.ulb
     errors.add(:transcendence_step, 'transcendence step too high') if transcendence_step > 5 && character.ulb
-    errors.add(:transcendence_step, 'transcendence step too low') if transcendence_step < 0 && character.ulb
-
+    errors.add(:transcendence_step, 'transcendence step too low') if transcendence_step.negative? && character.ulb
   end
 
   def over_mastery_attack
-    errors.add(:ring1, 'invalid value') unless ring1["modifier"].nil? || atk_values.include?(ring1["strength"])
+    errors.add(:ring1, 'invalid value') unless ring1['modifier'].nil? || atk_values.include?(ring1['strength'])
   end
 
   def over_mastery_hp
-    unless ring2["modifier"].nil?
-      errors.add(:ring2, 'invalid value') unless hp_values.include?(ring2["strength"])
-    end
+    return if ring2['modifier'].nil?
+
+    errors.add(:ring2, 'invalid value') unless hp_values.include?(ring2['strength'])
   end
 
   def over_mastery_attack_matches_hp
-    unless ring1[:modifier].nil? && ring2[:modifier].nil?
-      errors.add(:over_mastery, 'over mastery attack and hp values do not match') unless ring2[:strength] == (ring1[:strength] / 2)
+    return if ring1[:modifier].nil? && ring2[:modifier].nil?
+
+    return if ring2[:strength] == (ring1[:strength] / 2)
+
+    errors.add(:over_mastery,
+               'over mastery attack and hp values do not match')
+  end
+
+  def validate_over_mastery_values
+    [ring1, ring2, ring3, ring4].each_with_index do |ring, index|
+      next if ring['modifier'].nil?
+
+      modifier = over_mastery_modifiers[ring['modifier']]
+      check_value({ "ring#{index}": { ring[modifier] => ring['strength'] } },
+                  'over_mastery')
     end
   end
 
+  def validate_aetherial_mastery_value
+    return if earring['modifier'].nil?
+
+    modifier = aetherial_mastery_modifiers[earring['modifier']].to_sym
+    check_value({ "earring": { modifier => earring['strength'] } },
+                'aetherial_mastery')
+  end
+
   def character
     Character.find(character_id)
   end
@@ -49,6 +69,124 @@ class GridCharacter < ApplicationRecord
 
   private
 
+  def check_value(property, type)
+    # Input format
+    # { ring1: { atk: 300 } }
+
+    key = property.keys.first
+    modifier = property[key].keys.first
+
+    return if modifier.nil?
+
+    case type
+    when 'over_mastery'
+      errors.add(key, 'invalid value') unless over_mastery_values.include?(key['strength'])
+    when 'aetherial_mastery'
+      errors.add(key, 'value too low') if aetherial_mastery_values[modifier][:min] > self[key]['strength']
+      errors.add(key, 'value too high') if aetherial_mastery_values[modifier][:max] < self[key]['strength']
+    end
+  end
+
+  def over_mastery_modifiers
+    {
+      1 => 'atk',
+      2 => 'hp',
+      3 => 'debuff_success',
+      4 => 'skill_cap',
+      5 => 'ca_dmg',
+      6 => 'ca_cap',
+      7 => 'stamina',
+      8 => 'enmity',
+      9 => 'crit',
+      10 => 'da',
+      11 => 'ta',
+      12 => 'def',
+      13 => 'heal',
+      14 => 'debuff_resist',
+      15 => 'dodge'
+    }
+  end
+
+  def over_mastery_values
+    {
+      atk: [300, 600, 900, 1200, 1500, 1800, 2100, 2400, 2700, 3000],
+      hp: [150, 300, 450, 600, 750, 900, 1050, 1200, 1350, 1500],
+      debuff_success: [6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+      skill_cap: [6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+      ca_dmg: [10, 12, 14, 16, 18, 20, 22, 24, 27, 30],
+      ca_cap: [6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+      crit: [10, 12, 14, 16, 18, 20, 22, 24, 27, 30],
+      enmity: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
+      stamina: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
+      def: [6, 7, 8, 9, 10, 12, 14, 16, 18, 20],
+      heal: [3, 6, 9, 12, 15, 18, 21, 24, 27, 30],
+      debuff_resist: [6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+      dodge: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
+      da: [6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+      ta: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+    }
+  end
+
+  def aetherial_mastery_modifiers
+    {
+      1 => 'da',
+      2 => 'ta',
+      3 => 'ele_atk',
+      4 => 'ele_resist',
+      5 => 'stamina',
+      6 => 'enmity',
+      7 => 'supplemental',
+      8 => 'crit',
+      9 => 'counter_dodge',
+      10 => 'counter_dmg'
+    }
+  end
+
+  def aetherial_mastery_values
+    {
+      da: {
+        min: 10,
+        max: 17
+      },
+      ta: {
+        min: 5,
+        max: 12
+      },
+      ele_atk: {
+        min: 15,
+        max: 22
+      },
+      ele_resist: {
+        min: 5,
+        max: 12
+      },
+      stamina: {
+        min: 5,
+        max: 12
+      },
+      enmity: {
+        min: 5,
+        max: 12
+      },
+      supplemental: {
+        min: 5,
+        max: 12
+      },
+      crit: {
+        min: 18,
+        max: 35
+      },
+      counter_dodge: {
+        min: 5,
+        max: 12
+      },
+      counter_dmg: {
+        min: 10,
+        max: 17
+      }
+    }
+  end
+
   def atk_values
     [300, 600, 900, 1200, 1500, 1800, 2100, 2400, 2700, 3000]
   end