Clear blocked passages — no cave-in required

Confirm the grotto source

Download from the official Prism Launcher page — not a random mirror tunnel.

Open More info

Expand the SmartScreen dialog until Run anyway appears at the threshold.

Step through only when trusted

Choose Run anyway, then finish the installer and settle into the vault.

Lay the VC++ Redistributable

Install the latest Microsoft Visual C++ Redistributable (x64) for your Windows build.

Reboot if prompted

Some systems need a restart before the runtime path settles into place.

Re-enter the launcher

Start Prism Launcher from the Start menu or desktop shortcut.

Open instance settings

Select the instance, then open Settings — each alcove keeps its own Java flame.

Assign a Java path

Point to a JDK or JRE that matches the Minecraft version (often Java 17 or 21 for modern packs).

Set memory headroom

Raise max memory for large packs, but leave air for the OS outside the cavern.

Preserve the old instance

Keep the MultiMC instance folder intact before you move anything across the passage.

Use Prism import

Choose the MultiMC / Prism-compatible import path in Add instance.

Re-light Java and accounts

Re-check loader version, Java path, and Microsoft account after the migration settles.

Confirm loader match

Forge mods need Forge; Fabric mods need Fabric. Mixed jars collapse quietly or loudly.

Match Minecraft version

A 1.20.1 mod will not run in a 1.21 chamber without a compatible build.

Read the log strata

Open the instance log and remove the first missing dependency or corrupted jar.