Magmortar is available in Pokemon Sword and Shield's first DLC pack the Isle of Armor.
The final evolution of Magby and Magmar can be obtained under special circumstances - here's how to get one.
Magmarizer
According to Magmortar's Bulbapedia page, you must trade a Magmar whilst it is holding a Magmarizer for it to evolve.
Previously wild Magmars would be found carrying a Magmarizer when caught.
Although things could be different this time around.
