Sulfur Game Endless Mode: How to Unlock and Survive

Endless mode is an endgame arena challenge in SULFUR unlocked by finishing the story campaign, accessed through a basement hatch in the church next to Arthur for the price of one stamp.

The mode places you in dedicated combat arenas where you face continuous waves of hostile creatures rather than progressing through standard story levels. Defeating the final boss of the main storyline unlocks the basement hatch entrance. Players who defeat the Witch see the game credits roll before gaining access to this post-campaign arena. As confirmed on the Steam store page and the official website, the action-adventure roguelite tasks players with surviving increasingly dangerous combat spaces while managing valuable inventory gear.

How Do You Unlock Endless Mode in SULFUR?

Endless mode unlocks permanently once you complete the main story campaign by stepping through the giant door that leads to the final encounter. After clearing the main narrative arc and defeating the concluding bosses, return to the church hub. A floor hatch appears directly beside Arthur that leads into the basement.

Entering this basement hatch costs exactly one stamp per attempt. Upon paying the entry fee, you drop into the arena where waves of hostile mobs spawn immediately. According to patch notes published on the official announcement: Ralphie's Repair Update!, enemies double their damage dealt every 20 stages, while their physical models scale up into gigantic threats.

How Do Stage Cards and Progression Work?

Experience shards are pickup items dropped by defeated enemies during endless waves that grant character level-ups. Collecting these shards fills your progress bar, prompting a card draft screen with multiple choices to improve your odds.

Upgrades appear across distinct categories that dictate your survival strategy:

• Permanent upgrades: Stat boosts such as +10 Maximum Health (adjusted from +25 in early patches) or movement speed increases that last for the entire session. These help you increase health over extended runs.
• Stage-only temporary buffs: High-impact perks like Infinite Durability, Infinite Ammo, and Double Damage. Following official balancing updates, powerful stage cards like Infinite Ammo and Indestructible last for three waves rather than an entire multi-wave stage.
• Spawns and utility: Instant heals, repair triggers, stamp payouts, and vendor summons like Ralphie.

When presented with unwanted options, you can spend rerolls to refresh the selection, banish unwanted item drops to keep the pool focused, or decline the card entirely to claim a stamp.

Which Weapons Excel in Endless Mode?

Weapon choices in endless mode require high base durability, large burst potential, or crowd-control utilities to handle swarms and boss spawns. The mode tests equipment wear heavily, making efficient gun builds mandatory for deep runs.

As demonstrated in the The Homie YouTube channel gameplay analysis of endless setups, the Catacoil Rapid X benefits from chain lightning scroll enchantments, bouncing electrical arcs between clustered enemies. Pairing it with oils like Tandem and Gemini offsets damage penalties while keeping durability high. High-tier oils like Late Boom provide flat damage increases of +30 at the cost of a 30% reduction to projectile velocity.

Heavy single-shot options like the Arbiter or high-tier best weapons rely on attachments like the sniper scope to stack critical hit chance. A critical strike combined with a Double Damage card can push single-shot outputs toward 50,000 damage, instantly eliminating dangerous stage bosses.

For utility, converting an Unknown rifle with Charm turns tough targets into fighting companions. Charmed enemies count as cleared units toward completing the wave requirement, allowing you to bypass dense swarms without expending standard ammunition reserves. If you run low on supplies, stocking backup weapons and crafting items via food recipes ensures your character survives unexpected health spikes.

Where does this guide's official Sulfur game information come from?

Official details in this guide follow Sulfur game on Steam, which describes the game in its own words.

SULFUR is a modern old-school action-adventure: Outsmart enemies, find treasure, improve weapons, harness powers. Delve deeper, find answers, make it end.

Sulfur game on Steam