During battle the first of the 3 icons at top left corner of the screen
The options at the top left of the Debug menu are to spawn enemies
There's a scrollable list of enemies not all are imp jar compatible and summoning the black dragon will distort the screen
The number value next to it relates to the level of the enemy and it's HP
The last button in order is to summon the chosen enemy select nine tail fox and repeatedly tap that button
Once you close the menu the battle will resume
Good to do this in a multi area dungeon so killing all enemies won't end the battle