The message is risque and can easily be misinterpreted. The joke is really an inside joke.
The front says "Hail Seitan! (Pentagram picture) Go Vegan".
The back says "666"
If you would like this shirt send to you, provide me with your snail mail address and I will try to get it off to you as soon as possible (though I cannot gurantee a date).
First person to reply wins this free prize!