Level 0 - Youthfully drawn
Level 1 - Plainly Drawn
Level 2 - Expertly Drawn
Level 3 - Adeptly Drawn
Level 4 - Cleverly Drawn
Level 5 - Deviously Drawn
Level 6 - Ingeniously Drawn
You can solo any of them. Just got to be careful soloing 5 and 6.
How easy it is depends on your skill. Just remember when soloing, rule number 1:
Always hide right when the chest comes up, just before the monsters spawn.
I always suggest having provocation for treasure hunting.