Character Boost Token

The Character Boost Token is a currency that allows players to create a new level 50 character on their account. To use this token, select the 'Create a New Level 50 Character' button in the character selection UI. The token cannot be used on pre-existing characters. This feature will be available with the Heroes Evolved content drop.

Source
The Character Boost Token can be purchased through the in-game Store or from the character select screen. It costs 3900 Protobucks.