The recently added Wave 3 update for Kirby Star Allies brought with it new Dream Friends and a new mode called Heroes in Another Dimension. However, this update also added a few other things that need to be unlocked first. One such thing is the new Soul Melter EX difficulty for the game’s boss rush mode, The Ultimate Choice.
To unlock this new difficulty, you’ll need to beat the game’s new Heroes in Another Dimension mode. This mode is significantly more difficult than the main campaign in Kirby Star Allies, so be ready for some tricky puzzles and tough boss fights. Once you’ve beaten this mode a single time, regardless of how many Friend Hearts you collected along the way, you’ll gain access to Soul Melter EX.
To actually play The Ultimate Choice on Soul Melter EX difficulty, go to the difficulty selection screen in the mode and scroll all the way up to Soul Melter. From here, hold up on the left control stick and hold down the Minus button. Keeping both of these controls held, press the A button, and Soul Melter will suddenly become Soul Melter EX. This is the hardest challenge in Kirby Star Allies, as it features all the hardest versions of each boss, including the new Parallel versions found in the Heroes in Another Dimension mode.