Treacherous Halls

Treacherous Halls (also called Spike Fortress) is a promotional e-Reader level for Super Mario Advance 4: Super Mario Bros. 3. Its official difficulty rating is ★★★★★, making it one of the more difficult e-Reader levels. Much of the level consists of stomping enemies over spikes to cross them. Many Piranha Plants also appear, as well as two Flurries, one of which has to be ridden to collect an Advance Coin and also a 1-Up Mushroom. Boom Boom is fought at the end of the level. It was initially released only in Japan, but it eventually became available internationally when the game was brought to the Wii U Virtual Console in 2016. The key art for the card featured Boom Boom.

Enemies

 * Grand Goombas
 * Giant Koopa
 * Colossal Koopa Paratroopa
 * Goombas
 * Koopa Troopas
 * Buzzy Beetles
 * Para-Goombas (red)
 * Piranha Plants
 * Venus Fire Trap
 * Flurries
 * Dry Bones
 * Koopa Paratroopas
 * Spiny
 * Boom Boom

New level elements

 * Flurry