Evil Sudoku Puzzles (Hell Level)

Updated 14 October 2026

Hell is Suuudokuuu’s hardest technique-graded tier — what most competitors call evil or extreme. A Hell board is defined by the reasoning it demands, not by how few clues it starts with: no Hell board can be finished with any technique Nightmare allows, so every one needs a forcing chain. Unlike the generated tiers, Hell is drawn from a bundled corpus of published hard puzzles, verified by two independent solvers before it ships, and every board still solves on our technique ladder without guessing. Expect to use every chain and coloring pattern first — X-Chain, XY-Chain, simple coloring and AIC — before a forcing chain breaks the deadlock.

What makes a puzzle Hell

A chain follows an alternating sequence of strong and weak links, starting from a candidate and working outward until it proves an elimination or a placement no matter which branch turns out to be true. X-Chain works on a single digit; XY-Chain follows a path of bivalue cells instead. Simple coloring assigns two alternating colours to a network of strong links on one digit and clears any candidate that sees both colours, and AIC generalises the whole family, mixing digits and cell types along one continuous chain. Hell starts where all of that runs out. A forcing chain assumes a candidate, a cell’s possibilities or a house’s placements, follows every consequence, and keeps only what holds in every branch — the Nishio, cell and region forcing chain pages walk through one of each. A board makes the Hell corpus only if its hardest step on the rating-optimal path is a forcing chain, and only if our ladder can still finish it, so no Hell board ever asks you to guess.

How hard is it, honestly

Our sample of 40 Hell boards measures SE (Sudoku Explainer) 7.6 to 8.1, with the Nishio Forcing Chain as the most common hardest step and the Nishio Forcing Chain as the hardest step anything in the sample reached. Be careful not to read the clue count as the cause: the same sample puts Nightmare at SE 4.5 to 7.2 with 25 clues, and some Hell boards start with more givens than that. This tier used to be built from 17-clue puzzles alone, and it rated no harder than Nightmare; selecting on the required technique instead is what separates the two. Our clues versus difficulty guide takes that argument apart properly, and the rating guide publishes the per-tier tables.

Where to go next

Finished a Hell board and want more? Infinity Sudoku serves the record puzzles — Everest, Platinum Blonde, AI Escargot — that sit past even our forcing chains. Not ready for chains yet? Step back to Nightmare Sudoku, which asks for the same reasoning with more of the grid already filled in. Prefer paper? Download the printable Hell sudoku PDF. Browse the technique index, especially X-Chain, XY-Chain, Simple Coloring and AIC, the how to play guide, the 17-clue sudoku guide, every tier on the Sudoku difficulty levels hub, or head home.