In Warhammer 4e casters can use channeling in order to gain success level prior to casting a spell. Success levels are essentially for every 10 you exceed the skill number you gain a success level and they keep piling up till you make a failed roll.

As a wizard I am trying to figure out how to calculate the probability of piling up enough SL's before failing channeling and suffering a miscast.

What I wish to ask if how can I calculate my odds of reaching a certain SL prior to suffering a miscast (Making a failed roll) and losing all of my SL? (Note that the system uses a d100 and you try to roll below your skill.)


2 Answers 2


Failing a single test does not mean you will suffer a Minor Miscast.

Channeling test are normal Extended Test (page 154), so you will add your SL to your current total, whether it is positive or negative. For example, if you have 4SL before the roll, and you roll a 81 against a 50, you will have only 1SL after the roll. But you will be able to continue channeling. Even if you reach negative SL, it just means you start again at 0 the next turn, without miscast.

To get a miscast, you can :

  • Roll a double on a success, triggering a critical channeling, allowing you to cast the spell regardless of your SL the next turn, at the cost of a minor miscast.
  • Fail at casting the spell after succeding on your channeling, for another minor miscast.
  • Roll a double or any roll ending with zero above your target, triggering a fumble and a major miscast. It is not said that you cannot continue channeling after that, but you will probably be busy with te miscast consequences.
  • Get interrupted and failing your Cool -20 test, losing all your SL and triggering a minor miscast.

As for the probability of these cases happening, it would depend on a lot of parameters, from your target to the CN of the spell and your talents.


Probability of miscasting with Channeling increases dramatically as the CN increases because your Wizard needs many rounds of channeling before they can cast the spell, which is made more risky when the Wizard does not have Atheyric Attunement. Without AA the Wizard always has a 10% chance of rolling a miscast when Channeling.

e.g. With a Channel skill 45% = you have 45% chance to add 1 or more SLs, a 3% to crit chance, 50% chance of wasting the round because your rolled failed, and 10% change to miscast which drops to 6% miscast if you have AA.

Because many spells (like Bolt with CN4) need 4SL, you'll likely be spending at least 2 rounds channeling which in turn increases the chance of miscast a lot. Spending 3 rounds to cast Bolt once, with significant risk of miscast each round shows why Channeling is not great.

At skill 55 = 55% of 1+ SL, 5% crit, 41% wasted round, and 10% or 5% miscast.

At skill 65 = 65% of 1+ SL, 5% crit, 31% wasted round, and 10% or 5% miscast.

At skill 75 = 75% of 1+ SL, 6% crit, 22% wasted round, and 10% or 4% miscast.

This is why many Wizards use Petty spells until they have AA and have increased their Channeling skill to at least 70%. And also why often it is better for a Wizard to just dump all their XP into Language Magic and just spam cast the spells, because Channeling has more inherent miscast risk than Casting.

To calculate the actual likelihood of casting a particular spell CN, you'll need a spreadsheet with inputs for your Channel skill, CN target, and AA level --- which is how I got to the rough numbers above.


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