4.5/5 stars. Rounded Down. I feel this is a legion that has finally found its pace and place in third edition.
Background.
Before the Heresy formally took place, the Thousand Sons were attacked by the Space Wolves and their homeworld of Prospero destroyed. Later analysis would prove this to be the first likely act of Horus under the subtle influence of chaos who subtly changed the wording of the Wolves' orders from that of capture and return, to wholesale slaughter. Of course, even before this, they had been censured at Nikaea for arcane practices and stood apart from their brothers. They took part on both sides of the civil war, but were ever few in number thanks to preceding events. Magnus would take his time to throw his lot in with the traitors though, and didn't particular re-surface until the Siege of Terra itself.
Armoury.
Achea Pattern Force Swords. Command and champions can take a force sword for a small price upgrade on a power weapon. Generally worthwhile.
Telekine Shift is actually really strong and a prime upgrade for a troops squad. Take a willpower check in order to gain anti-grav and move through cover and literally run where you want during a rush. Played well, this is an objective snatching game shifter!
Aether and Asphyx weapons are contained in legacies. In general these are bolt gun and extra warpfire upgrades that grant you rending. All of them are worth considering, but they do come at the price of a shorter range. But presumably you are already in position somehow? The points cost is steep though for a full unit of bolt guns, bolt pistols, or support squad of aether-fire blasters.
Tactica.
Cult Arcana returns to make all models psykers and WP+1 in the advanced characteristics. This is entirely appropriate. All unit can (not must) be given an upgrade from the arcana, and this is absolutely what you should be doing. Note as well that perils of the warp has been tidied up here to just 1d3 wounds for the unit which is totally acceptable.
Raptora can have a crushing grasp weapon for tank killing which is excellent and a kine shield as a reaction to provide 4+ cover. This is a great choice overall.
Pyrae gives inferno shield that inflicts d6 S=4 hits if anyone hits them. This is okay but not great. Burning Grasp gives some breaching at high strenght and AP=3 which is solid.
Pavoni have a Stoneform reaction giving T+2 which is incredibly strong. The Bloodboil weapon is a 2+ poisoned attack which has AP=2 and is very likely to kill. A strong choice for the arcana.
Corvidae provides 5+ rending with Fated Shots, so who needs the asphyx weapon upgrades. Paths of Consequence meanwhile gives -2 movement to the enemy and forces a dangerous terrain check. This is also great!
Athanean grants Clarity to remove tactical statuses and Enamation of Dread as a weapon is a good ranged weapon that inflicts panic. Useful.
Gambit.
Prophetic Duellist switches in your willpower (which is hopefully high) instead of your focus roll (which might be lower after bonuses) to allow you to get the focus. A great utility gambit.
Additional Detachements.
Proserpine Convocation is really a grab bag of troops, elites, fast attack, and heavy transport. I suppose its utility is simply its broadness!
Advanced Reaction.
Fortress of the Mind means a 3+ invulnerable save against shooting attacks but drops to 5+ if you fail the requisite willpower check; plus you take perils. A useful way of staying alive when needed.
Overall then the Thousand Sons in third edition give you massive tactical flexibility whilst allowing you to also hone in on specialising your troops. Want an assault squad to crush a vehicle - take Raptora. Want a breacher squad to simply just sit there on an objective and take shots at higher toughness - take Pavoni. There's all sorts of things you can pull off beyond this of course. You just need to think hard about tailoring the arcana to the unit and what that unit's purpose is (tank killing, elite killing, backfield troop killing, objective sitter, ablative wounds for a named character, utility choice, and so on). I genuinely like them, but you have to plan ahead with your army building.
