Aura

Auras are special Mods. They operate as normal mods except that they affect the entire Cell.

They can be fused to create a stronger effect card. Using Aura cards will add to your total mod capacity, unlike regular mods. Forma can be applied to the special Aura slot the same way you would polarize any other slot. When clicking on Polarize to open the menu the aura slot will be to the left of the warframe slots and outlined in gold.

Putting an Aura with the same polarity slot as your Aura slot will double the mod points given (point cost 5 Rifle Amp becomes 10 points added) and Auras of different polarity will decrease the amount of points you gain (you will still gain more points regardless). A maximum of 14 bonus mod points can be acquired from a like-polarity Aura and 5 points for an unlike-polarity Aura.

You can add an Aura mod to your Warframe regardless of its rank, including unranked. This can help greatly when using a new frame, allowing you to use powers or other mods right away.

There are currently 3 2  and 9  aura mods.

Acquisition
Aura Mod cards were converted from user's Artifacts as of Update 9, including more than one if the user obtained more than one before the update. Most can be obtained as alert mission rewards, although some newer ones (listed in description) can be found in the Orokin Void or the Orokin Derelict. Aura cards can be sold for 500 credits at their base values.