Verified for patch 16.8.1

Solo Leveling

For the next 5 combats, your team size is 1 but the champion you field has massively increased stats. Gain 1 XP for every kill they get. Afterwards, gain 2 item components.

Effects

ADBonus: 0.5
APBonus: 50
ASBonus: 0.5
DamageAmpBonus: 0.3
DurabilityBonus: 0.2
FlatHealthBonus: 525
NumCombats: 5
NumComponents: 2
OmnivampBonus: 0.2
XPPerKill: 1

Solo Leveling enables

Xp On the Menu

The player-side progression resource. Spending gold on XP buys it; each level raises the team-size cap and shifts shop odds toward higher-cost champions. Augments grant XP directly or trigger off "level up" to accelerate the curve.