Tenet Weapons
- Main article: Tenet
Tenet weapons are special Corpus weapons.
Ranged Tenet weapons carried by a player's Sister and can be acquired once the Sister is Vanquished. If the player has enough weapon slots, they can claim these weapons from their Foundry, bypassing the supposed Mastery Rank requirement on these weapons. The weapons vary in attributes, dependent on the Sister the player has slain. The Energy Color on the weapon is depicted by what elemental bonus was augmented on the weapon during Sister creation and the progenitor Warframe. All weapons have an equal chance of spawning from a Sister.
Tenet Tetra - Greater magazine; can eject its entire clip into a grenade.
Tenet Flux Rifle - Enhanced fire rate and range, but uses clip magazine instead of an auto rechargeable battery.
Tenet Arca Plasmor - Longer range before damage falloff occurs and shots ricochet off surfaces.
Tenet Cycron - Beam can chain to multiple enemies.
Tenet Detron - Higher critical and status chance; can burst-fire its entire clip.
Tenet Plinx - Higher damage, critical chance, and status chance; can launch a projectile that pulls in enemies before exploding.Certain ranged Tenet weapons are unique to Sisters, and are not based on existing, usable Corpus weapons.
Tenet Envoy - Fires rockets that become laser-guided while aiming; auto-reloads when holstered.
Tenet Diplos - Akimbo automatic pistols that can engage a lock-on mode while aiming to burst-fire seeking projectiles; auto-reloads when holstered.
Tenet Spirex - Shoots projectiles with extreme speed; headshots speed up reloading.Melee and Speargun Tenet weapons are not obtained from Sisters, and the former are not based on existing, usable Corpus weapons. Instead, they can be bought from Ergo Glast of The Perrin Sequence in any Relay for 40 
Corrupted Holokeys each (regardless of standing with The Perrin Sequence syndicate). Each offering has a random progenitor bonus damage type and percentage increase, which is cycled every 4 days at 0:00 UTC. Only one of each weapon can be bought per rotation.
Tenet Agendus (MR 14) - Hammer and shield whose heavy attacks launch energy disks.
Tenet Exec (MR 16) - Heavy blade with slam attacks unleashing multitudes of shockwaves.
Tenet Livia (MR 14) - Two-handed nikana that builds blocking angle from blocking; pauses combo duration when holstered.
Tenet Grigori (MR 14) - Two-handed scythe with heavy slide attacks releasing ricocheting energy disks; pauses combo duration when holstered.
Tenet Ferrox (MR 16) - Upgrades to critical, status, fire rate, magazine, and explosion radius at the expense of damage; holding down fire button immediately charges the next shot.
Mechanics
A Tenet variant of a weapon will only provide mastery points once. A second weapon of the same variant but with a different Sister name will not provide extra mastery. These weapons have a max rank of 40. To obtain the maximum rank, the player must polarize the weapon five times, with each Forma increasing the maximum possible rank by 2 (similar to 
Paracesis).
The Tenet weapons additionally have bonus damage of one damage type, ranging from 25-60% of the weapon's base damage determined randomly, with lower percentages being more common.[1] The damage type of this bonus damage is determined by the Progenitor Warframe, as per this table.
Note: This additional bonus damage applies as weapon base damage, meaning elemental mods and status that scale from base / modified base damage will be affected.
Valence Fusion
Valence Fusion combines two of the same Kuva or Tenet weapons into one with a higher Elemental Bonus, multiplying the highest bonus of the two weapons by 1.1, capping at 60% bonus. Valence Fusion can be found under the Actions button while modding a weapon. After selecting Valence Fusion, a player is required to choose another of the same Kuva/Tenet weapon from the inventory (not in Foundry or with the Kuva Lich / Tenet Sister) to fuse it with. If the weapon's element bonuses differs, the player will be prompted to choose between the two available elements.
Any other properties (Orokin Catalyst, Forma, Stance Forma, Exilus Weapon Adapter, or Focus Lens) do not transfer over, meaning the order of fusion is important. Put simply, it is best to equip the weapon with the most resource investment (weapon rank, Catalyst, Forma, and Exilus that you wanted to keep) and fuse other weapons to it.
After selecting the donor weapon to be used in the fusion, a confirmation screen displays the desired weapon's new damage type and bonus values and warns that the transfer will consume the selected donor weapon. Players are then prompted to type FUSE to confirm the fusion.
- Example:
Kuva Kohm (A) has 40% Heat Damage and an Orokin Catalyst. Kuva Kohm (B) has 52% Radiation damage. The player has two options, to fuse (A) with (B) or to fuse (B) with (A).
- Since 52% is higher than 40%, the result will always be according to the percentage of (B) and multiplied by 1.1, resulting in 57.2%.
- Fusing (B) to (A): Equip (A), under Valence Fusion, select (B). The result of this will be a Kuva Kohm with 57.2% Heat or Radiation damage with an Orokin Catalyst. (B) will be destroyed.
- Fusing (A) to (B): Equip (B), under Valence Fusion, select (A). The result of this will be a Kuva Kohm with 57.2% Heat or Radiation damage without an Orokin Catalyst. (A) will be destroyed.
For Weapons and same-tier Armaments, maximum % bonus (60%) can be achieved in the following number of fusions:
| Minimum Initial Value | Maximum Number of Fusions |
|---|---|
| 54.6% | 1 |
| 49.6% | 2 |
| 45.1% | 3 |
| 41.0% | 4 |
| 37.3% | 5 |
| 33.9% | 6 |
| 30.8% | 7 |
| 28.0% | 8 |
| 25.5% | 9 |
| 25.0% | 10 |
For example, a Tenet Envoy with a 43% Toxin bonus will need at most 4 Fusions to reach the maximum element bonus of 60%.
Ephemera
Sisters have a 20%[2] chance to be created with an Ephemera equipped that corresponds to the Progenitor Warframe who created them. Players will receive a Sister's Ephemera regardless of whether they Vanquish or Convert them.
| Element | Ephemera | Visuals |
|---|---|---|
 Impact
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 Heat
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 Cold
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 Electricity
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 Toxin
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 Magnetic
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 Radiation
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Hound Companion
After vanquishing Sister, players will also get a fully built version of the Sister's Hound as a companion, and will also drop a random Hound component blueprint for all players in the squad which can be assembled with assistance from Legs in Fortuna. The Hound component blueprints are tradeable between players. Converting a Sister will not yield these rewards.
Ally
Converted Sisters can randomly appear in missions after the player enters bleedout, fighting alongside the Tenno. The converted Sister's level follows the formula Sister Rank x 20 (capped at level 80 in normal mode and level 135 in The Steel Path) regardless of mission level, their weapons have a 3x damage multiplier, and will use all of their abilities. They will stay for a minimum of 2 minutes.
Railjack Crew
With Intrinsics Command Rank 8, Converted Sisters can be brought aboard Railjacks as Crew members.
Unlike NPC crew members hired from Ticker, the Sister cannot be given weapons and will default to using their own, cannot operate Railjack systems such as the pilot seat, turrets, and repair, do not have moddable stats, and are restricted to the Defender role. However, their health and shields are significantly higher than NPC crew members, making them built for endurance and quite suited for repelling boarders.
Sisters as crew members follows a different level scaling formula compared to randomly appearing converted Sisters: Sister Rank x 15. For example, a Rank 5 Sister will be at level 75 when they are equipped as crew members.