The problem with Ricin is that it appears to be pathetically simple to make, it can be delivered in a number of ways, it is highly toxic, and there is no antidote. Instructions for the making of Ricin have been found online both in English and in Arabic. A few notable examples:

The Mujahedeen Poisons Handbook

A slick, professional e-book, distributed with its companion explosives handbook. Found inside a .zip archive on what at one time was a prominent Jihadist site. The first .zip file contained two more .zip files, inside of which were the two manuals.

Ricin-making thread on an Islamist forum

Earlier in this thread the author, Delphine, noted that Ricin was deadlier than Anthrax.