BaldursSpire 0.3.0

Six Baldur's Gate 3 companions climb Slay the Spire 2: Astarion, Shadowheart, Karlach, Gale, Halsin and Lae'zel. Each has 36 card types, a ten-card starter deck, upgrades, its own reward pool and a signature relic: 216 card types total. All reward cards are available from the first run, with no progression unlocks. The compendium exposes the full pools immediately. Starter-only Basic cards still come from the starting deck rather than ordinary rewards.

New in this version

144 additional cards support poison and evasive attacks, divine wards and curses, rage combinations, spell chains, druid forms and fighter tactics. New effects include attacks against every enemy, repeated strikes and Poison.

One-for-one BG3 replacements cover 110 native enemy models across every currently supported act: normal encounters, elites, summons and bosses. Each mapped model has a distinct BG3 identity and its own sprite. See enemy-replacements.md for the full mapping. Meet cranium rats, worgs, gnolls, kuo-toa, hook horrors, undead, githyanki, Sharran justiciars, infernal creatures, steel constructs and more. Boss replacements include Auntie Ethel, Dror Ragzlin, Grym, Raphael, Ketheric Thorm, Cazador, Viconia, Orin, Ansur and the Netherbrain.

Enemy signatures add Poison, fear, psychic pressure, exposed defences, armour, rage, ambush preparation or necrotic recovery to actual combat moves, with corresponding intent indicators. Native attack cycles, encounter slots, HP, summons and boss-phase state remain the foundation for saves and multiplayer synchronization. These are BG3 adaptations, not exact D&D rules or wholly rewritten boss fights.

A startup log records initialization stages and failures when the host exits without sending a crash report. It records no credentials or companion installation path. Unused native model-conversion and C++ runtime startup dependencies have been removed; BG3 package reading uses the bundled managed libraries.

Raphael offers three opening bargains. Karlach begins combat with 2 Strength; Astarion draws 2 extra first-turn cards; Shadowheart heals 5 HP after victory. Gale's Skills grant Vigor. Halsin starts with 5 Block and can enter bear form, then return to druid form with healing cards. Lae'zel starts with 1 Dexterity and combines tactical attacks, parries, Weak, Vulnerable and Vigor.

Play

Requires Windows, Steam Slay the Spire 2 version 0.107.1, and an installed Baldur's Gate 3. Melty installs BaseLib and BaldursSpire into the host's native mods folder and configures BG3's location. On first launch, select Load Mods and restart if the host requests it. Select a companion from the roster.

Ability records and icons are read from the player's BG3 installation at runtime. No extracted game assets or game executables are included. Original painted artwork accompanies the mod. Companion and enemy illustrations are static; some secondary companion scenes retain the host's Ironclad presentation.

Every co-op player needs both games and the same release. Use Multiplayer > Host and Multiplayer > Join through the host's native Steam lobby service, up to four players. Automatic Melty joining is not claimed. Two native ENet game instances on this PC joined one lobby and synchronized a Spirit Guardians play: both reported enemy HP 38, 36, 36. This verifies local native co-op, not a second Steam account or remote Steam relay connection.

Verification and startup reports

Compilation and specification checks pass for six companions, 216 cards and 110 enemy replacements. In-host checks pass for all card models, base values, upgrades and artwork, fresh-profile availability, every enemy replacement name and visual, and 12 boss map resources. Spirit Guardians damaged three real enemies; a cranium rat attack dealt damage and applied Frail. Grym and Orin encounters loaded and native enemy moves resolved. A cold generated-cache launch reached initialization ready in 15.9 seconds with the unused native libraries absent. Boss map texture suffix handling was corrected and retested without resource-load errors. Melty installed the release and completed two two-minute runs with startup, responsiveness, no-crash and loader-error checks passing. Its custom-host detector could not independently verify mod loading. Recorded interactive play was 20 and 15 seconds, below its graduation threshold; native in-game checks separately verified mod loading and gameplay. Native UI play also resolved a Divine Ward (one energy spent, five Block) and a full enemy turn. Full-run balance and every individual card interaction are not established by these checks.

Melty recorded two quick-close reports across 0.1.0 and 0.2.3, about 32 seconds after launch, without crash logs. Their cause is not confirmed. A normal Melty baseline launch reached the main menu; a private shell-launched lab encountered a separate Steam initialization failure. Neither observation proves those player reports fixed.

Initialization evidence is written to %LOCALAPPDATA%/BaldursSpire/startup.log. Explicit validation mode uses a separate throwaway profile and writes results and game-only framebuffer captures under %LOCALAPPDATA%/BaldursSpire/validation. It is disabled during normal play.

Source and credits

Made by Kyle. Original code: MIT; remixing allowed. Source and data sheets accompany the package. Dependencies: BaseLib by Alchyr, LSLib by Norbyte, and their compression/runtime dependencies; licenses and notices accompany the package. Development uses the Microsoft .NET SDK, ILSpy and universal-modder by rehan-remade. Original painted artwork was generated with OpenAI's built-in image generation tool from the individual creature descriptions in the enemy sheet, requesting full-body, left-facing, transparent dark-fantasy sprites. Baldur's Gate 3 and Slay the Spire 2 remain owned by their respective creators; this code license grants no rights to their content.