One umbra forma
You may not forma aura polarity to save a forma and get you prefered aura mod.

Helminth first ability since it's pretty crappy. I choose Eclipse to gain damage (+265.5% damage) while in light. i would recommend this one or roar. You have enough survivability with this frame, even in steel path or w/e "hard" content. More damage mean less enemies uptime and less damage taken overall. Best defense is offense :'D