Verrone's Obsidian is one of the darkest dahlias out there. It looks like little stars in the garden. This plant produces a lot of stems in the season. 
 
Colour: Burgundy/Black
Form: Orchid
Bloom Size: 4”
Plant Height: Medium (3' to 4')
 
Oops... skipped picture day! If you would like to see what this variety looks like, below is the link to google images.
 
verrone's obsidian dahlia - Google Search