Dungeon Assault (Dead Dungeon Book 5)

The strange, alien invaders were unlike anything seen before, wielding powers that let them defeat the dungeon's minions with ease. Yet, the dungeon is stronger than ever after overcoming these devious threats. Its master and minions both enjoy new strength as the dungeon expands to deeper levels.
The Master enters the dungeon's mysterious inner sanctum to search for an edge against his new foe, but unexpected events lead him to discover that his connection to the dungeon goes back to a period long before he was born.
One thing is for certain - now is the time for action. The enemy dungeon lord made a grave miscalculation by attacking his dungeon. Now it's time for punishment.