If there was ever a psychic power “taylor made” for Thunderwolf Cavalry, its the Endurance Power in the new 7th edition Biomancy discipline.
Given that TWC have multiple wounds per model and have high Toughness, it really enhances them, preventing them from losing entire models to ID weapons (i.e. S10, Force Weapons, Wraithcannons with Distort, etc) and also greatly increasing their overall survivability against torrent of fire attacks.
For example, with Endurance cast on them, it takes an average of:
(2/3 to hit)*(1/3 to wound)*(1/3 failed armor save)*(1/2 failed FNP save) = 27 BS4 bolter shots to cause a single unsaved wound on a TWC model (or 54 bolter shots to kill a single full model)
(2/3 to hit)*(5/6 to wound)*(1/2 failed FNP save) = 3-4 BS4 Plasma shots/Lascannon/melta shots to cause a single unsaved wound on a TWC model (or 6-8 plasma shots to kill a single full model)… this doesn’t take into account any cover saves or if the TWC have Storm Shields, which makes them 66% more survivable against these attacks (it takes an average of 22 Plasma/Lascannon/melta shots to kill a single Stormshield equipped TWC with Endurance)
Similarly, in close combat, even PFs would have a very hard time killing TWC:
-It would take a WS4 opponent (1/2 to hit)*(5/6 to wound)*(1/2 to fail FNP)*(2Ws per model with EW) = 9-10 PF swings, on average, to kill a single TWC model WITHOUT a Stormshield
-It would take a WS4 opponent (1/2 to hit)*(5/6 to wound)*(1/3 to fail 3++)*(1/2 to fail FNP)*(2Ws per model with EW) = 24-27 PF swings, on average, to kill a single TWC model WITH a Stormshield
As you can, see getting a squad of TWC with Stormshields, led by Wolf Lord on his own TWC mount, with Endurance cast on them is a pretty ridiculous combination that will have even the ultimate gun-line armies (i.e. Tau, IG, Eldar) struggling to bring them down.
Now, there are a number of downsides to fielding this unit:
1 – Points – By the time you buy TWC, Stormshields, a kitted out Wolf Lord, and a Biomancy Psyker, you are have likely spent a third of your armies’s points for about 5-7 models
2 – Melee – This unit requires getting into close combat to make its points back. Given that it is virtually impossible to do turn one (unless your opponent goes first, foolishly moves within charge range of your TWC unit, and your roll lucky charge distances; the odds are pretty stacked against this), then this unit will spend at least 1-2 turns (or even more, if your opponent is highly mobile and skilled at evading combat) not making any direct impact on the game. This can still be exploited either by seizing objectives that he abandons while fleeing your TWC unit, using the unit to absorb all the dangerous enemy firepower (thus freeing the rest of your army to do the real damage unmolested), and/or using the threat of your TWC deathstar to “shape” your opponent’s actions and make him do maneuvers that set up your overall strategy.
3 – Unpredictable Dice – This whole strategy is predicated on getting getting Endurance cast on your TWC reliably each game turn. You can take a Psyker and you can take TWC/Wolf Lord, but with a Rune Priest you only have a 16% (or 33% with ML2) chance of getting Endurance when rolling for you discipline. Taking a second Rune Priest increases your chances (and your number of Warp Charges for use in the psychic phase), but still you have at best a 33% + 33% chance of rolling Endurance on the Biomancy table, which is not the best odds to count on.
Now, say you do manage to get Endurance. Since it is a 2 Warp Charge power, you will need to commit multiple WC dice (like 5-6) each turn to get it off reliably. Since it is a blessing fortunately your opponent can only deny it with 6+s, so even if he has Tzeentch spam army with 15 Warp Charges, it will difficult for him to deny.
Finally, while Endurance has a respectable 24″ range, TWC are fast and will quickly get outside the Psyker’s casting bubble if you are not careful. Since it is a blessing, unfortunately your Rune Priest cannot ride behind them in a Rhino and cast it through a Troop Hatch, but must instead dismount and footslog while casting on the TWC. This can be mitigated by drop-podding the Rune Priest(s) in the vicinity where you are going to send the TWC, allowing him to be within casting range most (or all) of the game. Alternately, you could give the RP a bike or JP and have him follow closely behind the TWC, either solo (a bit dangerous) or with an escort of Swiftclaws/Skyclaws (somewhat increasing the overall “price” of the Rune Priest for increased durability against enemy shooting).
These are all things to consider when looking to field TWC with Endurance. As mentioned, the biggest potential pitfalls are getting the power in the first place and then reliably getting a WC2 power off every turn. This may be a bit heretical for the Sons of Russ, but probably the best bet from a purely competitive point of view is to take an allied Ultramarine detachment with Tigurius as the HQ. With PML(3) and re-rolls for his selections, he can MUCH more reliably get Endurance and, with his re-rolls of failed Psychic Tests, he has a very respectable insurance policy about getting the power off each turn (plus, as PML(3), he can combine with a Rune Priest to give you a very decent Warp Charge pool out the gate each Psychic phase).
Alternately, if you and your opponents allow FW, take Red Scorpions Sevrin Loth from the IA books… with PML(3) and the ability to simply pick (i.e. no rolling for them) Biomancy powers at the beginning of the game, he gives you Endurance 100% of the time and also a strong chance to activate it each Psychic phase. As discussed earlier