Work in progress

All-purpose build. (Eidolon build here)

• Natural Talent is my personal preference, granting a more fluid gameplay.
• For highlvl purposes, I'd recommend replacing [Natural Talent] with Adaptation. You could also swap in an Augment mod of your choice. Primed Vigor may be added if you're a veteran player.
• In terms of capacity efficiency, Constitution can be replaced by Augur Message; and a regular Flow does its job just fine.

• [Lasting Covenant] (Augment mod) lets you prolong [Harrow]'s crit buff with your headshot kills. I don't like it since Covenant (4) cannot be recast while it's still running, thus preventing you from recasting its squad immunity buff.

• Shields? Yes. [Harrow] is one of the very few frames I prefer playing with extra shield capacity. Penance's (2) buff duration scales with the amount of shields it consumes. Condemn (1) replenishes shields and overshields. Arcane Aegis and/or Barrier support shield regeneration during combat.
  TIP: If you're using a Sentinel or Moa pet, the Guardian mod will instantly refill your shields to 100% after using Penance (2)!

• Range? Covenant's (4) range equals your affinity range (in most cases 50m) and is not affected by mods. Condemn (1) and the range in which allies will gain energy generated by Thurible (3) are affected by range mods. If you feel like pumping energy into your squad mates nonstop, a range build might be your thing...

Questions? Feel free to message me ingame or via Discord. :)
Warframe tips and beginner's guide here.