Thallium

It has the chance to damage and slow enemies on hit.

Tactics
Keep in mind that Thallium does not stack, so purchasing more than one is pointless. Best used with a high hit rate to boost chances of triggering.

Trivia
The description may be a reference to Thallium poisoning, which is known to be slow-acting, painful and easy to misdiagnose.

Gallery
Thallium