Monsters require experience using wands before they can hit with them

It takes time for an early-game monster to acclimatize itself to the
power of an attack wand: in much the same way as a nervous human may
quite possibly miss with their first attempt to use a gun in combat,
an early-game monster will always miss on its first use of an attack
wand (but from then on will understand how they work and get over
their nerves, and will hit as normal).

This is a balance change based on observed results from tournaments:
guarding against deaths to early-game attack wands requires an
unusually cautious playstyle which isn't much fun (and might not
always be possible even for the best players), so it is quite common
for them to be the cause of random deaths that it wasn't worth trying
to avoid. Although trying to dodge a monster who found an attack wand
is fun, you only actually get that fun if something makes you aware
of the danger: the monster missing with the wand is a clear way to
demonstrate the danger and let the player know that now is the right
time to take precautions.

This change could theoretically have broken saves, but probably
doesn't due to there having been a spare bit in struct monst.  Just
in case, it is being pushed together with other save-breaking changes
to avoid the need for multiple bumps to EDITLEVEL.

doc/fixes3-7-0.txt

@@ -2908,6 +2908,7 @@ the game now automatically tracks which sell prices and buy prices you have
         and can also be shown elsewhere using the new 'price_quotes' option
 new shields: shield of shock resistance, shield of drain resistance
 new wand: wand of stasis
+early-game monsters always miss with their first use of an attack wand
 
 
 Platform- and/or Interface-Specific New Features