SPOILER ALERT - MAIN STORY SPOILERS - SPOILER ALERT
The second-to-last mission offers a unique piece of wargear, depending on which of your Sergeants was the Traitor.

• The Sergeant with the highest Corruption is the traitor
  
• If no Sergeants have 4+ Corruption, Martellus is the Traitor
  
• If multiple Sergeants have the same corruption level, the one with lowest Will Disciple is the Traitor

Several pieces of the dropped warger are useless to your remaining Sergeants, and must be donated to receive a powerful replacement item.
The picture below provides an overview of the available rewards.
[Transcript]
Martellus - Gift of the Iron Traitor - A servo-arm

• USELESS!
  
• Donate to receive Blade of Steel, a legendary power sword with ranged damage resistance, and a chance to instantly destroy vehicles.

Thaddeus - Pact of Thaddeus - A Sigil

• Gives +4 Corruption. No other effects.
  
• Donate to receive Caution of Thaddeus - a purity sigil which grants redemption, as well as bonus armor and energy.

Jonah Orion - Snare of Orion - A Force Staff

• USELESS
  
• Donate to receive Death Mask of Jonah - a purity sigil which grants redemption, as well as an aura that damages nearby demons, and restores energy to nearby allies

Avitus - Lost Honour of the Blood Ravens - Terminator armor

• USELESS (Only Avitus can equip it)
  
• Donate to receive Hour of the Blood Ravens - Terminator armor that grants massive health, melee skill, and ranged accuracy.

Tarkus - The Blighted Bolter - A Bolter (!?)

• Gives +4 Corruption. It has properties similar to the bolter usable by Thaddeus throughout the campaign. But this version can be used by anyone with bolter privileges
  
• Donate to receive Holy Bolter of Purification - a bolter with massive damage, high accuracy, and bonus Strength Discipline.