Ambush Prey

You channel primal predatory energies to perfectly conceal your presence in order to surprise your target, you become invisible for the times duration, granting advantage on all dexterity (stealth) checks to remain hidden, the invisibility will last for the duration of the spell however moving 5 ft or more from your position when you cast the spell, will end the effect.

as long as you remain invisible the first attack you make against any target who is unaware of your presence deals an additional 1d6 points of damage, this attack ends the spell 

AT HIGHER LEVELS: when you cast this spell using a spell slot above second level, the damage of your first attack increases 1d6 for every slot above second level.