Patience

Patience is one of the SOULs that fell into the Undergound, it was captured by Asgore to break the Barrier, but the mission ultimately failed. Due to Determination not being captured in the end. The Toy Knife was the weapon of the Patience SOUL human, and it's the only weapon that can be found at the start of the game, which is the Ruins. This possibly means that the Patience lost their weapon in the Ruins.

Trivia

 * The number of this SOUL is unknown, it could be one of the first ones.
 * Their weapon is the first weapon found in the game, excluding the Stick, since Frisk has it from the start of Undertale.