One of these builds is the Agathys Abjurer, which combines the Abjuration Wizard subclass with the Armor of Agathys spell from the Draconic Sorcerer. This combo produces an incredibly tough Wizard ...
Firstly, they pick up one level in Warlock for Armour of Agathys ... you see—Mage Armour's an abjuration spell, and Bouch will be taking several electives in Wizard for the subclass ability ...