The Necrosphinx is a Tomb Kings construct, that built to mimic and combine the appearance of creatures that inhabit the Nehekharan underworld, in keeping with the Tomb Kings obsession with death and the afterlife. This might mean they are mean to be Dread Abyssals, but given the setting was destroyed, we'll never know for sure.
The Necrosphinx is a Giant stone statue that the Tomb Kings animate during times of war to stomp and slash grave robbers trying to nick their stuff. Unlike the mythological Sphinx, the Necrosphinx has the torso and arms of a man, on top of a Lions body, instead of just being a human head on a lion (it also lacks tits), so it's more of a "Sphinxtaur". It also can't decide if it want's to be a rip off of the ancient Egyptian sphinx with it being a symbol for power and a Guardian, or if it wants to rip off Greek mythology, as it has wings (the truth is it's a mix of both since GW are lazy gits like that).
The Necrosphinxes were made during that time while the Tomb Kings were still alive and fleshy, with the Necorosphinxes being a combination of several different mythical creatures that dwelt in the Nehekharan underworld, with the genius idea that it would make a super killy monster. Unfortunately they absolutely scared the willies out of the Mortuary Cult as it was seen as bringing undead monsters out of the afterlife and into the real world (the irony was completely lost on them), and after a century of famine and plauge, the Necrosphinxes were blamed for cursing the land, and so were buried to hide them away forever. That was until a couple thousand years later when a massive Orc Waaagh was heading straight for Kemri, and was smashing aside everything the Tomb Kings were throwing at it. Setrra, re-awakened and in one of his moods, told the Mortuary Cult to dig up and animated the Necrosphinxes near Khemri and threatened to bitch slap the first priest who made an objection. So a group of rather frightened priests began the ritual to awaken the buried statues, and a week later they burst from the ground and began to RIP AND TEAR the Orcs. Afterwards they were deemed too valuable to be left under the sand and were dug up and moved back to the cities to serve in the Tomb Kings undead legions. The Mortuary cult is still terrified of them and actually thinks that they aren't animated by the souls of dead warriors, but are actually used as avatars of the Nehekharan gods of the underworld (Pha'a and Usekph) to take out their anger on the living world.
Despite being so scary, the Necrosphinx probably fight in one of the most unintentionally funny ways in the lore. Firstly they jump into the air and glide (yes those wings actually let them fly) over the enemy unit that has particularly offended them on that day, before dropping out of the sky like a brick and tearing its opponents apart with the blades stapled to their arms (you may think I'm embellishing the facts for humour, but this is pretty much how they're described as fighting in the 8th edition armybook).
On the Tabletop
The War Sphinx and the Necrosphinx are two versions of the same kit and mainstays of the Tomb Kings army back in the day. Unlike the War Sphinx, the Necrosphinx wasn't a mount option.
Total War Warhammer
The Necrosphinx is the anti-Large, monster killer version of the Khemrian War Sphinx. Does not Fly in this version, at least not for very long: it has a tendency to dash/fly through mobs when it attacks, often leading it to forget that it's fighting the Dread Saurian and go for the tarpitting Skinks instead.
Also you can somehow get milk from them: they count as something with 'six limbs' to get Centigor milk from when playing as Grom the Paunche. (Though granted this may be because of the poison in the stinger)
|Forces of the Tomb Kings|
|Leaders & Characters||Tomb Prince • Tomb King • Liche Priest • Liche High Priest • Tomb Herald • Necrotect • Tomb Monarch|
|Troops||Skeleton Archer • Tomb Guard • Skeleton Warrior • Nehekharan Warriors • Tomb Swarm • Dust Goblin • Bone Giant • Skeleton Horsemen -Skeleton Horse Archer • Carrion • Necropolis Knight • Mummies • Scythans • Bastethi|
|Constructs||Sepulchral Stalker • Ushabti • Warsphinx • Necrosphinx • Hierotitan • Tomb Scorpion • Bone Thrower • Screaming Skull Catapult • Casket of Souls • Necrolith Bone Dragon • Khmeric Titan • Sky-Boats|