Tendrils of Tzeentch
by Avian
One of the primary reasons for taking a Daemon Prince over a Sorcerer Lord in a Warriors of Chaos army is the Chaos Gift, the Tendrils of Tzeentch, which lets you re-roll one of your casting or dispel dice per turn and which can cause irresistible force (or a miscast, though in that case it is more a case of failing to avoid a miscast) and the equivalent when dispelling. But just how good is it?
Chance of reaching the various casting values using a given number of dice
For these figures, the given number of dice have been roll and if the result is too low or if a miscast happens, the lowest dice is re-rolled. Note that because there is never any point in re-rolling a dice other than the lowest, you can only get a Miscast with the Tendrils if you originally rolled more than two 1s (in which case getting something else on one of them doesn't help) or if you roll two 1s, re-roll one and get another 1. With five dice, the former is actually slightly more likely and when it happens you will at least not have used your Tendrils re-roll for that turn.
| Number of dice | ||||||
| Casting value |
1 | 2 | 3 | 4 | 5 | Suggested # of dice |
| 3+ | 88.9% | 99.5% | 98.4% | 96.5% | 93.8% | 2 |
| 4+ | 75.0% | 98.1% | 98.4% | 96.5% | 93.8% | 2 |
| 5+ | 55.6% | 94.9% | 98.4% | 96.5% | 93.8% | 3 |
| 6+ | 30.6% | 89.4% | 97.9% | 96.5% | 93.8% | 3 |
| 7+ | 0.0% | 80.6% | 96.9% | 96.5% | 93.8% | 3 |
| 8+ | 0.0% | 68.1% | 94.0% | 96.3% | 93.8% | 4 |
| 9+ | 0.0% | 52.3% | 89.5% | 95.9% | 93.8% | 4 |
| 10+ | 0.0% | 35.6% | 82.5% | 94.8% | 93.7% | 4 |
| 11+ | 0.0% | 19.9% | 73.1% | 92.6% | 93.6% | 4 |
| 12+ | 0.0% | 7.4% | 61.7% | 89.0% | 93.2% | 5 |
| 13+ | 0.0% | 7.4% | 48.8% | 83.5% | 92.3% | 5 |
| 14+ | 0.0% | 7.4% | 36.0% | 76.1% | 90.6% | 5 |
| 15+ | 0.0% | 7.4% | 25.0% | 66.9% | 87.8% | 5 |
| Miscast | 0.0% | 0.5% | 1.6% | 3.5% | 6.2% | |
If we compare them with the odds for casting spells normally, we can see a few interesting things:
Firstly, the chance of miscasting goes drastically down, while the chance of successfully casting a spell goes up by about the same amount. This is because failed casting attempts when you are rolling a lot of dice are mainly cause by Miscast and if you had simply added up the sum of the dice, the score would probably have been high enough. In fact, the chance of miscasting with Tendrils of Tzeentch is about the same as miscasting when rolling two dice less and not having Tendrils. By taking the Tendrils, you can happily throw five dice at a spell attempt without much worry. This I see as the primary advantage of the item. If you also have the Infernal Puppet, to modify the few miscasts that get through, you should be laughing.
The secondary advantage is that the chances of getting spells off increases by about 20%, a little dependant on casting values and dice. Quite often, having the Tendrils is better than having an additional dice in terms of getting the spell off (and that is not even considering the reduction in miscasts). In fact, when you consider that Tzeentch characters need to roll 14 or more to get Gateway off, the odds of casting a spell with five dice and Tendrils never drops below 90%, which is pretty much unheard of.
As a rule of thumb, you can cast spells where the casting value is equal to the average roll with one dice less than you intend to use, with 90% reliability. For example, the average result on four dice is 14, and with Tendrils you can cast 14+ spells with one dice more than that (i.e. five dice) with a roughly 90% chance.
Irresistible Force - what about that?
I have not shown the odds of getting irresistible force in the table above, because the odds of getting it depends on what risks you are willing to take. The table just assumes that you re-roll whenever the casting roll fails for whatever reason, but it is quite possible to re-roll one of the dice even if you pass the casting roll. Let's say you make a try at Infernal Gateway with four dice and roll 2, 3, 3 & 6. You have reached the casting value (with a +1 to cast granted by the Mark of Tzeentch, you get 15), but the spell can still be dispelled. You can try re-rolling the 2 in the hope of getting a 6, to make it Irresistible, or at least a higher number to make it more difficult to dispel, but if you roll a 1 you have now just failed the roll where you previously had made it. How willing a player is to make risks like this will influence the chance of getting Irresistible Force, but there are some other factors to consider.
As suggested, trying to get an Irresistible Force might mean that you now fail the casting roll. This chance is generally quite slim, but it is there. On the bright side, re-rolling can't cause a Miscast unless the original roll was a Miscast to begin with. Thus as the chance of Irresistible Force goes up a bit, the chance of getting the spell cast goes down a bit. The odds of getting Irresistible Force will be in the region of 20 to 25% with five dice.
It is worth noting that the improved chance of getting Irresistible Force with the Tendrils of Tzeentch is much less impressive than the reduced chance of getting a Miscast. This is because it is much easier to roll anything but a 1 than it is to roll a 6 (to put it a little simply).
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