Seven Star Tattoo
Original Seven Star Tattoo
There is no Seven Star Tattoo (SST) in the original series.
The inspiration to create it was out of the filler episodes about Hoshigakure and their "star meteor" they'd train with to gain exceptional skills and obtain a purple chakra that was stronger than anything they knew.
Constant use did wear the body down.
Seven Star Tattoo in SL
The tattoo starts with a base you can obtain, and you have to get the ink for each star in order to complete the tattoo.
Like the name, you need 7 stars.
A complete tattoo will boost your powers and obtaining all the ink is extremely difficult.
Tech Facts (SPOILER!)
After you fight a certain individual at the forest, you will obtain the raw base of this tattoo.
Note that you cannot get this tattoo if you are already having the Curse Seal - you will be repelled. Evil characters won't have a chance for it either.
After the first star, you have to ask the local tattoo shop who will tell you then to collect ink ... that ink is a random drop in certain events(forest/village). The chance is pretty slim.