Venom, is a shortsword and was enchanted in Kydan's preferred "thrice-charmed" style giving it three different magical aspects.
First it bears a +1 enchantment giving a bonus to attack and damage.
The second enchantment is the ability to poison. If used to strike down three intelligent enemies, living or undead, it gains the ability to inflict a deadly poison (as the spell) on a successful strike. The magical nature of the poison allows it to affect any enemy be they living, undead, or a construct. It can hold up to three doses of deadly poison, although this does require it dealing a death blow nine times, three for each charge. The poison is exceptionally potent and becomes more potent per charge held. Each one in the blade at the time the power is invoked causes the victim to suffer a -1 penalty to their saving throw. For example, if only one dose is in the blade the target suffers a -1; but if it has all three doses in it the target suffers a -3.
The third enchantment is a defense against poison. When holding Venom's hilt, its bearer cannot be poisoned, but will be aware of the attempt. Further, if Venom isn't already holding its maximum allowance of poison doses, one of them becomes charged. So, if Venom has only 1 dose left in it and the owner is poisoned, the poison has no effect and it gains a second dose that can be used as desired. Venom doesn't need to be drawn for its protective nature to work. But its master must have a firm grip on its hilt to work.