The mass bonus that turns a charge into a monster truck, now attached to an attack she can use every five minutes.
Carl did the arithmetic on Crowd Blast out loud. Katia Grim killed Hekla with the base Rush. The upgraded version adds a wide cone of collateral damage and drops the cooldown from a day to five minutes. And with her wrestling belt bonus on top, it would be the equivalent of hitting someone with, well, a monster truck.
The belt's mass-doubling is what makes her charge a siege weapon rather than a tackle, and its interaction with the new riot kit is the reason Carl concluded that troll or not, the fan box gave her exactly what she needed.
A gaudy championship wrestling belt worn under armour, doing arithmetic nobody watching would guess at.
Katia's mass multiplier and the hidden term in every damage calculation she makes.