How to get Knell Prime Blueprint in Warframe?

Knell Prime Blueprint is an item dropped from Void relics.
You can find the list of relics below, and click on the links to see how to get them.

Relics dropping Knell Prime Blueprint

• Lith B11 (Common) - Vaulted
• Lith S14 (Common) - Vaulted
• Meso N12 (Common) - Vaulted
• Meso S13 (Common) - Vaulted
• Meso V7 (Common) - Vaulted
• Axi B5 (Common) - Vaulted
• Axi P4 (Common) - Vaulted
• Axi W3 (Common) - Vaulted