In The Stormlight Archive, the sentient sword that consumes Investiture is Nightblood.
Nightblood is an awakened sword originally created on Nalthis, the world of Brandon Sanderson’s novel Warbreaker. Its creators attempted to reproduce the effect of a Shardblade through Awakening, using a powerful Command and a vast quantity of magical Breath. The result was a living weapon with a strong personality and a destructive interpretation of the command to destroy evil.
When drawn on Roshar, Nightblood consumes Investiture, including Stormlight. It can drain power from its wielder and from its surroundings, making it extraordinarily dangerous to use. Its effects are more extreme than those of ordinary Shardblades, which are associated with the Knights Radiant and the spren of Roshar.
Nightblood first appears in The Stormlight Archive through connections to characters from Warbreaker and later becomes especially important in Words of Radiance and subsequent books. Honorblades are ancient weapons associated with the Heralds, while Sylphrena is the nickname of Syl, a sentient honorspren—not a sword.