How to Co-op in Sephiria

Quick answer

Sephiria supports online co-op for up to four players through Steam. The host creates the run and controls the lobby; guests join through the invitation or session route available to them. Decide who is carrying which weapon plan before rewards begin, because shared rooms make duplicate weaknesses more expensive.

Before the lobby

Check	Host	Guest
Game version	Confirm everyone is patched to the same version.	Restart Steam or the game if the version display differs.
Session route	Create the lobby and keep the invite visible.	Accept the invite or join through the host's session.
Roles	Explain the first weapon direction and reward priorities.	Bring a weapon you can control without needing every drop.
Connection	Test the lobby before a serious run.	Close duplicate sessions and retry from a fresh invite.

A clean session flow

1. The host starts the lobby and invites up to three friends.
2. Everyone confirms the same game version and selects a Costume they can use under pressure.
3. At the first reward, announce the intended weapon direction instead of silently taking every item.
4. Trade only when the recipient can activate the item; a rare object is not useful if it breaks the other player's route.
5. When a teammate goes down, clear enough space before attempting the revive.
6. Before a boss door, compare health, MP, inventory room, and escape tools as a group.

Trading without breaking a build

Use a simple rule: offer an item to the player whose current weapon or trigger can use it immediately. If the item is only a future possibility, keep the run stable first. One player should also call out shared route decisions so the party does not split its rewards across incompatible combo families.

Revive and recovery habits

The safest revive is created by controlling the room first. A ranged player can clear a lane, a guard-focused player can hold pressure, and the downed player's partner can position near the revive without pulling a new wave. Do not trade two more downs for a fast rescue when the room has not been stabilized.

Connection fixes

• Recreate the lobby after a failed invite instead of stacking repeated invites on a stale session.
• Confirm Steam is online and that every player can open the game normally in single-player.
• Remove incompatible mods before testing whether the base lobby works.
• If only one player fails to join, have that player restart Steam and accept a fresh invitation.
• Record the exact error, game version, host region, and party size before asking the community for help.

Party build planning

Give each player a job: reliable damage, control, sustain, or safe revival. Use the Build Planning page for the main route and the Boss Route Guide for the final inventory check. A party with four identical damage plans often has less room for recovery than a party with complementary jobs.

Next step

Start with the Beginner Guide if the shared inventory rules are unfamiliar, then compare Weapons before hosting a longer run.