|Level||Cumulative cost ( Ancient Souls)||Effect (Bonus to Kumawakamaru)|
Borb is the most important outsider by far. Only Borb and Kumawakamaru decrease Monsters Per Zone, which directly impacts your progress by a massive margin.
Borb's effect decreases Monsters Per Zone(MPZ) by a large margin. Once Kumawakamaru, Ancient of Shadows maxes out at 3743 levels, Borb is the only way to decrease MPZ. Maintaining 2 MPZ is important because of an effect called "Instakill." Once a player has the DPS to kill a monster in less than one frame, the death animation of the first monster for the next zone is reduced to one frame. This causes progression at 2 MPZ to be nearly 9x faster than progression at the ambient 10 MPZ.
Furthermore, there are many mechanics in the game that buff the damage statistic. However, Borb and Kumawakamaru are the only two mechanics in the game that reduce the Monsters Per Zone statistic. As the amount of monsters determines the amount of time spent on a zone during progression, Monsters Per Zone is a very important statistic to minimize. As Kumawakamaru has a level cap, as mentioned above, Borb is a driving factor in progression.
Borb was added to the game in Patch 1.0, and originally increased the maximum transcendent primal reward. In the Patch 1.0e10 update, the transcendent primal cap was removed, and Borb's function was then changed to increase the effectiveness of Kumawakamaru.
Borb started out in patch 1.0e10 as 10% effectiveness of Kumawakamaru per level. In 1.0e11, this was changed.
Each of the outsiders that buffs an ancient is holding one of the platonic solids.
Borb is holding the sphere, which represents God.