<-- ya, that's right.
Pyromancy is always fun, just not as fun in 40k... Nearly all these powers have some Soul Blaze granting ability which is really pretty bad. On a 4+ you get D3 S4 AP5 wounds on the unit/model. Extra wounds are always nice but you have an essential BS3 roll to hit and then the usual to wound, etc. It's nothing to complain about but it's nothing you'd jump up and down and want for your army either. So, Space Marines, Dark Angels, Grey Knights, Chaos Space Marines and Imperial Guard can take this discipline. Let's see what they're getting...
Primaris - Flame Breath. A heavy flamer with Soul Blaze. Not terrible - mass Destructors for Warlocks are often great but there are better damaging powers in most armies psychic arsenals and such template weapons can be bought as, well you know, weapons.
1 - Fiery Form. A Psyker based blessing which grants them a 4++, +2 strength and the Soul Blaze ability with his close combat attacks - i.e. a decent challenge man but most Psykers are pretty crap in combat already with a base of 2W. The new CSM Sorcerers could break this mould but I find this unlikely and thus this is a pretty bad power.
2 - Fire Shield. Unit based blessing with a range of 24", this grants a unit a 4+ cover save that do not have the special rule Soul Blaze or Melta. Not sure why this exception was needed... They do however have a sort of reversed Hammer of Wrath ability where if a unit charges them successfully, they take 2D6 S4 hits at I10. Not too bad on a leading/bubble-wrap unit in the open. You're ensuring they get a 4+ cover save against most weapons and doing more damage in combat.
3 - Inferno. A 24" small blast with the soul blaze and ignores cover special rules. It's a Frag Missile which ignores cover and sets things on fire - it sounds so much better than it is unfortunately. Again, this isn't really doing much that a bog-standard weapon cannot do nearly as effectively, particularly given the cover changes of 6th edition.
4 - Spontaneous Combustion. A actually decent sniping power (focused witchfire) which inflicts an automatic wound against a model with no saves/cover allowed. If slain you get one of those Inferno blasts (minus Soul Blaze) centred over the model. This is a great way to remove important models from an opponent's unit and for doing an extra little bit of damage but since the wound is automatic and only invulnerable saves can be made, the power skips a lot of defensive steps and thus makes a good sniping tool.
5 - Sunburst. Our first nova power. This hits all enemy units within 6", does 2D6 S4 AP5, ignores cover hits with the Blind effect. Not stupendous damage but decent against Guardsmen-like models but Blind on multiple units is pretty nice. Even a Space Marine unit fails this 1/3 times, Guardsmen 1/2 times. The only issue here is the 6" range - anything higher would be insanely powerful but ensuring you get a model into range of multiple units with so short a range is hard, particularly if you want the psyker to live until the next turn. In the end this restriction makes this more likely to be a one-off power rather than something you continually force your opponent to defend against.
6 - Molten Beam. Our first Warp Charge 2 power which means only Mastery Level 2 psykers can cast this and it uses two charges. It also means anyone without Mastery Level 2 cannot randomly roll this power so it makes the other powers a bit more reliable to get. To the actual power... it's a Blood Lance like beam but with a set range (12") and the melta rule instead of Lance. That's pretty good but Warp Charge 2 limits its application as does the beam property - you're unlikely to get two good melta hits in against enemy vehicles unless you're right up against one due to the ranges involved. More often than not this is just another meltagun as a psychic power which can poke more models behind the initial target (and is thus more effective at anti-infantry). The fact that it's a Warp Charge 2 power really hurts as well - you'd need to pay 50 points on average to get this power when you can get a lot more meltaguns for that cost.
Conclusion - A lot of these powers can be replicated by Imperial infantry. Flamers, missile launchers and meltaguns. Really only Fire Shield & Spontaneous Combustion are anything you'd want and Fire Shield is worse than the Overwatch Divination power. Since neither of these powers are the Primaris and most of the armies are Imperial (i.e. can take most of these powers as weapons already), there's not much advantage to taking this discipline (though would Xenos really want it either?). A Grey Knight Librarian is probably going to benefit the best if they're packing a Force Sword - they can use Moltenbeam and is in an army which could benefit from more Melta and Fiery Form isn't as bad when it turns the guy into a S7/2+/3++ due to the Force Sword and Hammerhand, etc. Still not a great option though and best left at home for something else.
Very thematic for all those fiery Blood Angel successor chapters though. Oh. Wait.
