Invoke

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The #invoke extended command allows you to activate certain objects. The only objects that can be activated this way are crystal balls and most quest artifacts.[1]

Artifacts tire after you invoke them, and you cannot do so again for rnz(100) turns (averages 100; can be up to 2000, but 95% of the time it is less than 400). If you invoke again too soon, "You feel that the <artifact> is ignoring you" and 3d10 turns are tacked on to the wait time.[2]

Optimal invocation schedule

Invoking strategy is basically a trade-off between the risk of getting nothing and waiting too long. The turns to wait after a successful #invoke versus probability of success are graphed below (assuming your experience is <=17):
waiting time after successful #invoke versus probability of success of invocation

If you need the artifact reliably, such as emergency healing from the Staff of Aesculapius, you should treat it like prayer - #invoke only in dire need. If you want a simple strategy for the most successful #invokations per turn, e. g. charging lots of wands with the PYEC, you should wait 78 turns between invocations. This yields an expected wait of 180.83 turns. If you miss the time a bit, the rate of success does not go down much. Your experience level does not matter.

The optimum strategy is waiting

82;81;68;81;88;67;54;96;78;62;88;81;65;63;81;65 

turns after consecutive failed #invokes and restarting the list after successes. This yields an expected wait of 180.2354 turns.

Robert Tupelo-Schneck, of liquid diet tourist fame, has computed these numbers.

Minimizing the expected wait between success is the same as maximizing the expected rate of success per turn due to the Renewal Theorem.

List of possible invocations

Invoking a non-artifact crystal ball is exactly the same as applying it.

List of possible invocations for new SLASH'EM artifacts[3]

References

  1. artifact.c in NetHack 3.4.3, line 1188
  2. artifact.c in NetHack 3.4.3, line 1198
  3. http://www.angelfire.com/trek/mazewest/spoilers/arti_007e6.txt

This page may need to be updated for NetHack 3.6.0.

It may contain text specific to NetHack 3.4.3. Information on this page may be out of date.

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