Klein bottle/Archive 2
Klein bottles can break in combat for two reasons. First, that your combat options are set incorrectly. To avoid breaking a klein bottle from combat actions you must set your attack setting in the tactics options to only use the hand that is not holding the klein bottle. For example, if you have the klein bottle in your right hand, you should set your tactics to only attack with your left hand with "tactics attack left"
It is possible to parry with a klein bottle as well, however this may result in the bottle breaking as a result of its condition reaching zero. To avoid this, as with the attack options, you should set your parry setting to only use the hand that is not holding the klein bottle. For example, if you have the klein bottle in your right hand, you should set your tactics to only parry with your left hand with "tactics parry left"
The second way a klein can break in combat is if you are hit in the hand that is holding the klein bottle, with an attack that is powerful enough. The threshold for this appears to be quite high, NPC's that are confirmed to be strong enough to do so are the Grflx queen and the Ephebian Citadel Guards. However with appropriate arcane shielding, the likelihood of this occurring is vastly minimised.