Sectumsempra is a spell from the book "Harry Potter and the Half Blood Prince". It is a spell that is said to cut you up. Hence the bloody looking design.
Start by printing "Sectumsempra" in one sheet of paper because it should have a larger font than "is a very messy spell". Use the picture provided to make your life easier.
Now repeat step 1 with "is a very messy spell". Use the picture provided to make your life easier.
Now using the exacto knife, carefully cut the letters out to make the stencil.
Repeat step 3 with "is a very messy spell".
Now place a bit of the red fabric paint into a small bowl. In this case I used the cap of the paint. Now add a few drops of water into the cap to thin the paint a bit. This will make painting easier and will also help give that bloody look.
For this part, just go crazy. Splatter the paint all over the shirt. If you're not feeling crazy, then just use the picture provided to help you paint the gash looking design.
Repeat step 5 with the black fabric paint.
Trace the stencil on to the shirt. Do this for both stencils. Fill in the letters with the black paint.
After, let the paint dry and follow further instructions on the fabric paint bottle. And there you go. An awesome Harry Potter inspired shirt.