An effortlessly nasty build. Perfect for battlegrounds, cyrodill soloing, or roaming the town as vermin. Stage 4 vampire for cost reductions and the powerful invisibility while sprinting passive. Pop simmering frenzy, start sprinting, and at 5 stacks either heavy attack or lotus fan and then blood for blood until one of you dies. Also, lotus fan stuns from stealth, so you can play sneakier and wait out an easy kill. That ranged stun is also basically the only way to kill alerting guards in thieves guild and brotherhood quests without being spotted.

I prefer to miss the sneaking vampire passive because it makes overworld sneaking so jittery, but it can be really fun to glide around while stealthing in PvP so that's up to you.
Simmering Frenzy is an easy sub based on situation too. I swap it for hypnosis in the overworld and siphoning srikes for PuG dungeons (normal difficulty only!) Soul teather is also a nice ultimate for crowd control, but not neccessary. Play around with slot 5 and your ultimate to find what you like, but remember to stick to magic damage for War Maiden.

Quite a fun combination of a stamina build that uses War Maiden, as Blood for Blood costs health to use, so Resolving Vigor is basically our sustain. By building stamina we also have more leeway for being stunned, rolling, and sprinting (in other words, surviving in PvP). If you get in real trouble though, roll, sprint and cloak, as resolving vigor won't keep you alive for long. Zoal head one piece is interchangeable with all sorts of monster sets (slimecraw/balorgh...) but if you let people see it in your outfit it can help intimidate them a bit by thinking you have the 2 piece. Also, it looks so gorgeous.

Vesture of Darloc Brae is the perfect QoL for this build too. Not only does it make overworld sneaking a breeze, it almost cancels out simmering frenzy while crouching, so you can build up to max stacks while perfectly stealthed and then strike from the shadows at the opportune moment without worrying about timing your health. It also means you can stealth for absurdly long, essentially as long as your potions last.
If you want to go full ganker though, sub it for Shattered Fate, and hope you never need to retreat.