About Dimension Invade PQ

There may be other bosses if you finish faster, but i have never reached those so no info Hope I helped

Actually, there are 3 different bonus stages.
If you finish under 10mins, you face Blackheart as a boss.
If you finish between 10-20mins, you get taken to a bonus stage where you kill mobs with high HP.
If you finish after 20mins, you get taken to a bonus stage where you kill weaker mobs.

After each of the bonus stages, you'll get a box that has a chance of giving you a medal (one medal per bonus stage).