Variant Armor Class Rules for Dungeons and Dragons 5th Edition
In D&D 5E, Armor Class is usually based on a character's Dexterity Score, and because Armor Class is such an important feature of your character, this can be a real problem for characters that have low Dexterity and don't want to die.
Below are alternative AC calculations for certain character types so that more builds are possible and more ways of thinking about defensiveness in combat are made rules-appropriate. Mechanically speaking, they also buff Martial characters and certain types of spellcasters who focus on melee. Where no change is listed, no change is made.
Natural Armor. 13 + your Constitution modifier. Tortles also use this calculation in this ruleset
Mage Armor. 11 + your spellcasting ability modifier. At Higher Levels. When you cast this spell at higher levels (which is not possible using the Armor of Shadows feature), the AC increases by 1 for every two spell levels above 1st.
Unarmored Defense. 10 + your Strength modifier + your Constitution modifier.
Medium Armor. Base Armor Class + 1/2 your Strength modifier (round up) + 1/2 your Dexterity modifier (round up).
Heavy Armor. Base Armor Class is reduced by 2, but you may add your Strength modifier to this number.