This Tournament:

Point value as I understand it
Targets across board: +(10)
Unusual Move-Type: +(10)
Aggressive: +(10)
Number of Abilities: -(1^1.5)
Number of Lines for Custom: -(0^1.5)
Unclearness to ability: -(10)
Total: 19 Points
Yes you explained the ability in the description but I would argue the clearness needs to be on the unit for this tourney since we lose points for having too many description lines on the unit.

As for the actual unit:

Creativity: 5/5 (New unit and new mechanic)
Theme: 3/5 (Backstab fits unit well, but why does an assassin have so many attack squares? Shouldn't it be mostly movement and backstab?)
Execution: ?/5 (I don't fully understand Backstab still, could you explain it more to me?)