A Hero Rush is a rare scenario introduced in What Did I Do to Deserve This, My Lord!? 2 where multiple heroes will enter the dungeon in sequence without a break, usually with a powerful hero at the end. They also form the gameplay of games like Yu-Nama: The Puzzle and No Heroes Allowed: No Puzzles Either!. With No Heroes Allowed! VR, Hero Rushes have been removed in favour of grand strategy-style gameplay instead.
In What Did I Do to Deserve This, My Lord!? 2 and No Heroes Allowed![]

The Hero Rush featured in Overlord Castle Gate.
In What Did I Do to Deserve This, My Lord!? 2, Hero Rushes are only featured in Overlord Castle Gate and Overlord Castle Garden, among the final areas in the game. Specifically, they take place on stages 6-2 and 7-4. The game gives a significantly longer amount of time than usual to prepare.
In No Heroes Allowed!, three stages feature Hero Rushes: 1-5EX, 2-7, and 3-8EX. In 2-7's case, it's the final stage of Ludgala Tower, meaning only one Hero Rush is ever present in standard gameplay. Hero Rushes can also be encountered during Dungeon-a-Day challenges.
Hero Rushes encourage the player to use more Dig Power than usual to spawn monsters during the confrontation phase, lest the heroes overwhelm the dungeon through sheer numbers. However, to offset this, there will be less heroes per wave than is expected at that point in the area, and the ones prior to the final group are usually quite weak. Regardless, it's good practice to remember what hero is coming next and set up a powerful monster for them, while the current one is being defeated somewhere else. Due to the amount of heroes entering and killing your monsters, there is a high chance that at least one will mutate into a Basic Breed. The Hero Rushes in What Did I Do to Deserve This, My Lord!? 2 are particularly taxing, targeting the God of Destruction with only Level 1 Breeds and heroes far above the level they are designed to fight. Ergo, in those scenarios, spawning Runeborn monsters like Blobs and Maras is mandatory to find any sort of success.
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In the puzzle games, Hero Rushes form the basis of their gameplay—as well as the story itself for Yu-Nama: The Puzzle—with 3 heroes per stage entering in sequence. The first two are usually weak and can be found in any stage of the area, while the final hero acts as a boss exclusive to the stage. In No Heroes Allowed: No Puzzles Either!, the second hero can sometimes be a Rare or Super Rare, encouraging the use of a Lilith's Song to capture them and use them to evolve monsters.