Derelethi Spiders

While there are hundreds, maybe thousands of species of poisonous spiders in Lustria, one of the unique is the derelethi spider. While the spider itself isn't impressive on the surface, it's neither the largest, nor the deadliest spider in the Lustrian jungles but it produces a very interesting by-product.
Derelethi venom is often referred to as "the poison that heals."
Most Lizardmen healers try to keep some derelethi venom on hand.
Derelethi spiders eat primarily poisonous insects or relatively small poisonous lizards and frogs.
By itself, Derelethi venom is poisonous, not enough to kill or permanently harm a man-sized creature but enough to make them sick. It will kill a small animal.
The unique property of Derelethi venom is that it neutralizes other poisons and other poisons neutralize it. So a skilled healer can use Derelethi venom as an antidote to other poisons. The key is to get the dose right, if you don't use enough Derelethi venom, the other poison will still take effect, but if you use too much Derelethi venom, you will poison the person you are treating with Derelethi venom. Though, since Derelethi poison is not lethal, Derelethis poisoning is preferable to lethal poison.
"The poison that heals" is sometimes viewed as a quasi-holy substance. With the right blessings, derelethi venom can be enchanted to be especially deadly to undead and daemons.