The Ulthar Clan were not so fortunate as the Crûsgar or Barundar clans. With the fall of the Dwarven Kingdom, the Ulthar Clan found themselves backed into a corner by the undead. Their only way out was to dig deeper. For centuries they dug to escape the plague, until they broke into a massive cavern system known as the World Cavern. After generations of being underground, this clan knows nothing else. They became the Deep Dwarves. Known to other races in the World Caverns as the Duergar. They know no humour or joy and live in constant fear and toil.
Deep Dwarves are much taller and thinner than their surface kin, almost as tall as humans. They average about 5 ft tall. They have dusky grey skin and hair. Many of their kind have been effected by their time in the lightless depths, dealing with arcane horrors and aberrations. Some have developed powerful minds and some have been broken by the constant stress, devolving into mad creatures known as Derro.
The Ulthar Clan has several subclans, including the Oremantle and the Ironlight.
These traits are in addition to the Dwarven traits found in the players handbook.
Ability Score Increase. Your Intelligence Score increases by 2
Superior Darkvision. Your darkvision has a radius of 120 feet.
Sunlight Sensitivity. You have disadvantage on attack rolls and on Wisdom (Perception) checks that rely on sight when you, the target of your attack, or whatever you are trying to perceive is in direct sunlight.
Duergar Magic. At 3rd level you can cast the enlarge/reduce spell on yourself once (enlarge only). At 5th level you can cast the invisibility spell on yourself once. You regain all uses of these spells after a long rest, or a short or long rest if you are in the World Caverns. Your spellcasting ability for these spells is Intelligence.