Venom from different creatures can harm or kill in different ways.
Some venom affects muscle, other affects the blood and others cause intense pain.
The following video details a few venoms and how they work. Just be aware, it can get a little gross, and there are some graphic images of wounds.
If you want to head right to the effects of box jellyfish venom on a toad's heart, jump to the four-minute mark.
The video is educational, and sometimes hilarious. When the host scares the camera operator to demonstrate how Irukandji jellyfish venom works by sending the adrenaline system into overdrive for half an hour or more, you're sure to chuckle.
Most of the video will make you look twice, or three times, when in the wild and water to avoid venomous critters.
And don't worry, the toad in the video didn't feel a thing. It was brain dead, but toad hearts, for some reason, have the ability to keep beating after the animal is neurologically dead.