Compound formed from concentrated sulfuric acid and sulfur
The reaction is given here.

$$\ce{S + 2H2SO4 → 3SO2 + 2H2O}$$

Sulfur react with sulfuric acid to produce sulfur dioxide and water. Sulfuric acid should be concentrated solution. The reaction takes place in a boiling solution.

$\ce{[S4]^2+}$, $\ce{[S8]^2+}$ or $\ce{[S19]^2+}$ is formed when sulfur is dissolved in oleum. The following is a paraphrase of an inorganic textbook.