From Twilight Heroes Wiki

Merit Badge:

Congratulations! It takes a special kind of hero to be willing to delay the benefits of training for an extended period of time, to the point that they can gain two levels at once. For your heroic patience, you have earned a patch!

You get a merit badge: Delayed Gratification

Merit badges can be seen in your character page.

Requirements

Acquired by leveling up twice in a row without leaving the trainer's screen at the Heroes' Guild. To see if you have enough experience, consult this chart.

• Note: This means you have to be able to get both of the levels from the Guild (levels 2 through 25).