The Vampiric Knight does not slink in the shadows. They are above mortals, those that are mere cattle to vampires, and have the pride and audacity to flaunt it. This is a front line warrior, who also wields the power of a true blooded Vampire Lord. As such, this build requires the Dawnguard DLC.
High Elf is chosen as the race, for the extra 50 magicka. The Ring of the Erudite, from the Rings of Blood Magic quest, grants an additional 100 magicka. With these two boosts, the Vampiric Knight is free to never level magicka. The first level up points go into health, until 200 is reached. Then pump stamina to 150. Finally, mix health and stamina level ups until you have 200 stamina. At that point, every single subsequent level up goes into health. OR, if you opt to use the master illusion spells, which are optional and mostly just for fun, put just enough levels into magicka to be able to cast the master spells.
Focusing on health and stamina solidifies the Vampiric Knight's role as a melee fighter. Wielding the Mace of Molag Bal, the progenitor of all vampires, the Vampiric Knight falls into one handed and shield gameplay. However, as a powerful vampire, their illusion spells are also 25% more powerful. Frenzy, Rout, and Pacify spells control the battlefield through manipulating the minds of the weak. Muffle and Invisibility are rare options, but remember this is not a sneak build. The knight is clad in full heavy armor, aspiring towards the Ebony Mail from the Boethiah's Proving quest, which is available at level 30. This armor adds to the dark and foreboding image of a vampire, and grants an aura of poison damage while fighting in melee. The amulet used is the Amulet of the Gargoyle, gotten from the Amulets of Night Power quest. This doubles the potency of the Summon Gargoyle spell that Vampire Lords have access to.
Vampire Lord form is a key aspect to this build. It provides the Vampiric Knight with a method of ranged combat, healing in combat, and pure power. This build is very much focused on the Vampire Lord form, and perks it out completely. The most powerful spell at the Vampire Lord's disposal is Vampiric Grip. This spell has an incredibly long range, if you can get the aiming down. The crosshair should be slightly above and to the right of distant targets to pluck them from far away and drag them into your swarm of bats and the claws of your summoned gargoyles.
The most important questline for this character is the Dawnguard main questline, which gets the Vampiric Knight their powerful ring and amulet artifacts, as well as the Vampire Lord form. While traveling with Serana, the Vampiric Drain spell is heavily reduced in power, so illusion spells and front line fighting are most useful in those parts of the game. However, the Vampire Lord still provides healing, the ever-useful Vampiric Grip spell, and can dish out damage with claw attacks. And always keep in mind that the other ring of blood magic, the Ring of the Beast, can be used when the 100 extra health and 20 extra claw damage is more useful than spells.
The Dark Brotherhood is also a fun line of quests to do with this character. But remember: the Vampire Lord does not cower in hiding. Sometimes invisibility can be used, and frenzy spells can get difficult targets murdered by throngs of their former allies. But the primary method of assassination is the same as Arnbjorn of the Dark Brotherhood. With no one in eyesight, the Vampiric Knight can enter Vampire Lord form and swoop upon the feeble mortals, eliminating the target and anyone else they so please to feast upon. Doing these quests gets a suitably ominous steed for the knight, in the form of Shadowmere.