Indiscriminate: When this character attacks an adjacent enemy, it ignores enemy abilities and commander effects that prevent targeting and attacking. These attacks cannot be redirected.

Dark Spirit: This character is an insubstantial spirit of pure Force. It ignores all terrain and can move through enemy characters (and enemy characters can move through it), as long as no character ends its move in the same space as another character. It cannot end its turn in a wall or solid object (a space bordered by magenta lines). It does not provide cover, and it cannot open doors nor hold them open. It cannot attack or be damaged, and does not count as a legal target, as the nearest enemy, or as adjacent to other characters. This character cannot score victory points for occupying specified areas in scenarios that include such victory conditions. It is not affected by commander effects.
During setup, choose a Unique allied character with a Force rating. That ally gains Force Renewal 1 and Sith Rage as long as it is within 4 squares of this character. This character is defeated if the chosen ally is defeated. Instead of making its normal attack or attacks, an enemy within 6 squares can spend 1 Force point to defeat this character. This character can avoid this effect with a save of 11.

So as long as Indiscriminate stays on melée pieces they can still never attack it, since they can only attack adjacent.

Actually Indiscriminate wouldn't even need to be restricted to Melee pieces as the definition for it singles out that it only triggers against adjacent enemies (regardless of melee attack).