Rogue-likes typically feature mechanics meant to challenge players after they have beaten the game. In Dead Cells, this takes the form of Boss Cells. Once you’ve defeated The Hand of the King, the third and final boss of your first playthrough, you will automatically pick up your first Boss Cell. This is how you will modify the difficulty of future playthroughs. Here’s how to do a one boss cell run in Dead Cells.
When you respawn back at the Prisoners’ Quarters, head to your collection area (the area where each item and power-up you’ve unlocked is housed in glass containers.) The giant middle glass tube now has an interact prompt, which allows you to tab back and forth between Normal Mode and Hard Mode. This is known as a “one boss cell” run — it reduces the number of health fountains you can use, increases the number and strength of normal enemies, and makes bosses slightly tougher by skipping their first phase.
However, you must play on “one cell” mode in order to unlock later difficulties — you can’t just farm Normal Mode and continually get Boss Cells. A useful weapon for clearing one cell is the Ice Bow. Invest in Green stats and upgrade your Ice Bow every opportunity you get — this weapon trivializes a lot of enemies. If you find a Legendary weapon of some kind, you can replace the Ice Bow, but otherwise don’t bother.