Senua's Sword is the original weapon Senua uses in combat.
Hellblade: Senua Sacrifice
How and when Senua acquired the sword is unknown, but she has possessed it long enough to handle it well. It is the only weapon she uses in combat against enemies.
Senua uses the sword to kill Valravn and Surtr to clear the path to Hela's Sanctum. When she first comes close to Hela's Sanctum, she brandishes the sword as Hela approaches her. However, Hela quickly knocks Senua away and sends her tumbling to the beach, shattering the sword as well. Senua uses the broken blade of the sword to cauterize a wound on her face, and then discards it. Until she acquires Gramr, Senua is left without a weapon.
When Senua anticipates a combat situation, she immediately draws the sword; the sword cannot be used outside of combat. Senua is capable of using a quick attack, a heavy attack, or a combination with the sword, and can also parry enemy attacks with the sword.