Warframe: Dagath

Blueprints for this headless horsewoman warframe are acquired from a room that must be added to your clan dojo called "Dagath's Hollow" and to build her you'll need a bunch of new things called vainthorns which only drop from the "locked" abyssal zone in Ceres, a place you might not even see unless you have the keys to access it. Each run through that zone needs you to use a key which you can buy from one of the "big 6" syndicates (Arbiters, Meridian, Suda, Perrin, Loka or Red Veil) for 5000 standing, and only if you are at rank 2 or above with them.

While the abyss mission itself is just a visually darker exterminate with eximus (strong guys) stronghold  activating about 2/3rds of the way through and an extra pick up and deliver a cursed lantern to extraction tacked on, you'll need to do this a decent number of times to get enough vainthorns to build her and even more if you want her pure slash whip-sword weapon.

Sounds like a pain to build her and it is, especially if you don't yet have a strong frame to grind out those components but she is very rewarding and a fun close combat frame to play as her abilities of spinning scythes (Yareli's only good move), adding viral, adding crits (+possible ghost form) and summoning a charge of ghost cavalry that absolutely wreck everything in a straight line all work very well together, with survivability coming directly from her passive that makes every 3rd health or energy orb 300% more effective. You'll want to be right in the thick of things to make the most of that. Dagath definitely gets my tick of approval.