Vanilla Fortress

Enter the fortress via a pipe, leading to an underwater section. Swim right, past the first ball and chain, and the second one at the top.

The route splits based on your Mario size.

If Small Mario only: Walk along the bottom under a set of spikes and enter the pipe. Head right, over and under two fish. In the open area, make the block drop, then swim onward as it rises. Hit the block to get a power-up. You can swim upward to face ball and chains with fish, or go right to face falling blocks, a ball and chain, and enemies. The top route is slightly easier and both routes merge later.

If Any Mario: Go right on the higher passage, past the ball and chain. At the spikes, stay below the ceiling to avoid fish. Grab the power-up from the block afterwards. Continue right to a ceiling with spikes; the brown ones fall after a brief shake. Provoke a falling spike by swimming under it briefly, then move out of its path as it falls. Stay in the middle to avoid enemies on the floor.

Enter the pipe. Go right, over enemies, and past a falling rock. Wait for the rock to fall, then go over it as it rises.

Head right and position yourself between the two ball and chains. Continue down the passage to a yellow ! block and the red boss door.

BOSS: REZNOR You face four dinosaurs on rotating platforms that spit fireballs. Hit each platform from underneath to defeat the dinosaurs. The ground disappears as you fight, so be quick. Hit one dinosaur off immediately. When the ground is too low to hit them from below, jump onto a rotating platform to hit the others. Dodge fireballs and try to defeat them quickly. A strategy is to knock one off, jump on its platform, and defeat the others as it rotates.

After defeating Reznor, save your game. A bridge will form to the right, leading to 'Butter Bridge 1'. This concludes the Vanilla Dome secret levels.