The Souls Rebound shoots special arrows which mark enemies they hit for 5 seconds. When a marked enemy is hit by the same player, a ding sound effect plays and the damage is stored. When the 5s is up, the ❁ Damage dealt during the marked time is totaled, increased by 1.2x and dealt in one blow.
Sleeping Golems in The Catacombs - Floor VI will not wake up from any hits while marked except if one of the effects shown above are applied.
The first arrow shot with this bow will not damage the mob until it's unmarked.
Using this bow on the Sven Packmaster and dealing enough damage used to be able to skip the second phase, allowing the player to kill the boss faster.
This has been changed since, and will display a message in chat reading "This mob is immune to Souls Rebound!"
This bow shares a similar name with one of Yone's abilities, Soul Unbound, from League of Legends. The ability marks enemies and "stores" damage based on damage dealt during the mark, dealing a burst of damage after the mark expires, which is similar to the Souls Rebound's ability.