False Friend — R.E.P.O. mimic

Experimental, unpublished 0.1.9 development build. Full in-game verification is pending.

False Friend is a custom impostor that copies a player, encourages a teammate to follow, and attacks after leading that teammate away from the group.

Implemented design

• Mimic encounter levels occur every two or three expedition levels, starting on level 2 or 3. On those levels natural spawning is always active with the mod: the first attempt starts as soon as the generated expedition is ready, with no probability roll or 38–65 second opening delay. Only one mimic is active at a time; a killed/removed mimic is replaced after three seconds. Shops, lobbies, tutorial and arena do not count. The floor schedule remains stable when the same save is reloaded.
• Placement prefers hidden, clear and reachable points roughly 9–18 metres from players. If those checks cannot find a point, automatic fallback searches walkable map positions and positions behind players. Fallback can relax visibility and the normal seven-metre separation while retaining navigation, body clearance and separation from players. Missing model/navigation readiness is retried every second rather than cancelling the encounter. No forced in-front spawn or testing toggle is required.
• Copies a living or dead player from the current lobby. Reuses actual player meshes, materials, rig and animation; checks cosmetics and colour changes every 0.5 seconds, including replacement avatars after respawn.
• Keeps the chosen player's identity until that player dies. After a live-to-dead transition it may choose a replacement only after two seconds in an empty, unseen room, with no living player nearby. Room overlap, current player rooms and line of sight are checked; unknown rooms prevent a change. A player already dead when chosen remains a valid locked disguise, and cosmetic refreshes never choose another identity.
• Targets living players other than the one it impersonates. This protection remains when the copied player is the last survivor of a multiplayer lobby. A genuinely one-person lobby permits targeting the copied player for solo testing.
• Drives walking and sprinting with the native player gait clips, with foot motion synchronized to distance travelled. Grab/bite poses are layered over the copied model.
• While disguised, turn speed changes in short bursts, with occasional mouse-like flicks and held glances. It pauses more frequently: typically 0.4–1.6 seconds after 2–5 seconds of walking, with occasional two-second stops.
• Occasionally hops while walking, using native jump/fall/land poses and jump/landing sounds. A clear-overhead check avoids ceiling clipping. These are render-only hops; navigation and the collision body stay on the ground.
• Replays short voice clips belonging to the copied player. Lure and attack recordings share a shuffled rotation: every currently available clip gets a turn before repeating, with no immediate repeat across reshuffles when multiple clips exist. New recordings join the rotation. Missing clips remain silent.
• Uses native R.E.P.O. robotic speech for "Come this way", "Over here", "Follow me", "I found something" and "This way".
• Recordings, robotic lure lines and the reverberating attack voice use normal player proximity attenuation and occlusion. Distant players do not hear them.
• Tries to lead a target away, then gives a 1.1-second warning before chasing. At close reach it performs a 1.8-second grab-and-bite: reach for 0.5 seconds, hold briefly, bite once at 1.0 seconds for 40% of the victim's maximum health including upgrades, then release. Damage rounds up to a whole HP (100 maximum HP means 40 damage; 200 means 80), and is based on maximum HP rather than remaining HP. The attack cooldown is 2.4 seconds from the start. Walking into a player alone causes no damage.
• If the lure has not succeeded after 45 seconds from its first lure attempt on that target, it turns back and chases that player to attack. Waiting, walking back toward the target, temporary stuns, or a safe disguise change that leaves the same victim eligible do not restart the deadline. The target, deadline and committed pursuit are replicated for authority changes. This committed pursuit survives loss of sight and distance; it ends when the target dies or becomes ineligible.
• Sharp upper and lower teeth reveal as the bite attack begins, track the jaw as it opens/closes, and hide again at release or interruption.
• During the grip/bite, the attack voice plays a recording belonging to the player being impersonated, with strong 2.2-second reverb. Pitch and recorded words stay unchanged. It uses no generated scream or other player's recording; if that player's clip is unavailable, the effect stays silent. Speak a few phrases during the session to populate the matching recording pool.
• The brief grab actually locks the victim's position at contact before the bite, rather than only slowing them. It blocks movement and jumping during the 0.5–1.3 second grip phase while preserving looking and item use. Dodging the reach, blocking contact or stunning the mimic interrupts it. The local lock has a hard expiry and releases on death, displacement, obstruction or session changes; it does not teleport the victim into the monster.
• Host-controlled movement, attacks and synchronized appearance identity. Physical impacts and active native weapon hit volumes can damage or stun the mimic.
• Includes one-player support, including a local microphone fallback when the native voice stream is unavailable.
• A living mimic no longer disappears just because four minutes have elapsed. It remains until killed/removed or the level ends.
• Press F6 during a level to open the testing panel, with Spawn In Front and Auto Spawn controls. Auto Spawn is off by default and resets off when leaving the session.

These are implemented code paths, not a claim that all behavior has passed in-game testing. See VALIDATION.md in the accompanying source deliverable for tested scope and outstanding checks.

Installation

Install BepInExPack 5.4.2305 and REPOLib 4.2.0 in a separate R.E.P.O. profile. Put FalseFriend.dll inside BepInEx/plugins/FalseFriend/ in that profile. Launch the profile modded. Every player must install the same version and matching dependencies.

The first encounter level is expedition level 2 or 3. Simply launch the profile modded and enter an eligible level: automatic spawning begins as soon as the map/player are ready and keeps retrying if assets or navigation are still loading. On encounter levels the director replaces a removed mimic after three seconds, with no fixed encounter cap. There is no natural encounter on level 1 or other unscheduled levels.

Solo testing controls

Launch the updated profile using Start modded and enter an expedition. Press F6 to open False Friend — Testing.

• Spawn In Front places a mimic about 1.5 metres directly in front of your current view, including on level 1. It uses your own avatar for predictable solo testing and bypasses the normal encounter interval, room clearance, minimum distance, visibility and path checks. It does not require a larger room.
• Auto Spawn is an optional forced-placement testing mode for unscheduled levels. It keeps at most one mimic active, waits 15 seconds between successful test spawns, and retries failed placement after three seconds. On a scheduled mimic level the automatic natural director takes priority, regardless of this toggle. The toggle resets off when leaving the session.
• Close the panel with Close, F6 or Escape to resume normal input. The controls work in singleplayer or for the host of a private lobby.

Normal encounter levels follow the two-to-three-level schedule whether the testing toggle is on or off. A manual test mimic occupies the single active slot; after it is gone on a scheduled level, natural encounters resume following the three-second replacement delay. Manual test spawns never enable natural replacements on an unscheduled level.

Testing Auto Spawn uses the same direct placement. A forced test mimic stays visible and can play voice lines even where the game has no navigation surface; it retries nearby navigation attachment once a second. Normal movement resumes when attachment succeeds. Natural encounters use navigable placement and their own persistent fallback search.

Voice recording

Let everyone in the lobby know voice replay is enabled. Short samples of the player's normal game microphone stream are held in bounded memory, retained across levels in that run, and shared only with other players in that lobby. Samples are cleared when leaving the session or changing rooms/saves. No recorded voices are included in the download, saved to disk, uploaded to a speech service or used to train a model. The game microphone device, mute, push-to-talk and volume settings are respected.

Successive recordings become locally available immediately. Multiplayer uploads are queued with a limit of eight pending clips and paced every 12 seconds; if that queue fills, the oldest pending clip is replaced. This avoids discarding every recording spoken during a transport cooldown. Speak several phrases to give the mimic a variety of matching clips.

Compatibility and current limits

Developed against R.E.P.O. v0.4.4.3 (Steam build 23363152), Unity 2022.3.67f2, BepInEx 5.4.23.5 and REPOLib 4.2.0.

Cosmetics inside the normal player visual hierarchy are mirrored; effects that require another mod's custom scripts or external visual objects need individual compatibility tests. This is a custom NavMesh creature, so interactions with third-party enemy mods, doors, stairs, weapons, host migration and late joining require real sessions before public release.

Credits and source

Code and package artwork were created with AI assistance. A public Thunderstore release must use the AI Generated category, alongside suitable mod/monster/audio categories. Native game content remains owned by its respective rights holders. See LICENSE and THIRD_PARTY_NOTICES.md.