^ As others have said, DOx is a series of drugs where there are several variants - the letter x being where each one differs. The most common DOx compounds are: DOB, DOC, DOI and to a slightly lesser extent DOM, but there are also others.
All of them are significantly different in effects, and often in dosage.
I would not consume it until you know which of the DOx series it is. If the person doesn't know, then it might not even be DOx and more likely they're just saying that it's SOMETHING other than LSD, which could be a whole host of things - and you shouldn't consume it. If they know and can tell you which one it is, you can check the
The Psychedelic Index linked at the top of the page (and here in my post) for that substance's Big & Dandy thread, go there, and read up more about it.
Be warned that the DOx substances usually last a lot longer than LSD for most people. People have had trips that have lasted as long as two entire days from high doses of some of them.
If you do find out what it is and get around to consuming it, definitely start with one blotter. You do NOT want to be stuck having taken too much with substances that can last so long - especially since the duration is very dose dependant, so taking 2 blotters is likely to last a lot longer than one.
Any additional questions?