Replication Issues

Replication Issues is a progression modpack for NeoForge 1.21.1, built around the Replication mod: 10 matter types, from Earth to Quantum, and each one is literally a chapter in the in-game quest book guiding you step by step — it's not just flavor, the order actually matters.

It starts small: smelting with Productive Metalworks, Andesite Alloy from Create, a trip down into the Undergarden for a Forgotten Ingot. From there Modern Industrialization carries you from a stone pickaxe to an electric motor, until Replication gets its own working Replicator online. Along the way AE2, Occultism, Ender IO, and Mekanism all come in, each one pulling the next forward — Mekanism's Enrichment Chamber, for instance, won't run until you've already got Iesnium from Occultism in hand.

Past the halfway point the pack gets serious: PneumaticCraft from end to end until you're manufacturing your own PCB, a custom portal to the Otherside (the only place Draconium spawns — no portal, no Draconic Evolution), and Ad Astra sending you across three planets chasing Desh, Ostrum, and Calorite to upgrade your rocket engines.

The End isn't stock either: there's a dedicated dungeon on Glacio guarding an item you need to track down before you can even think about opening the portal — the whole system was rebuilt from scratch for this pack. From there it's Draconic Evolution up through Chaotic, Avaritia up to the Infinity Ingot, and the real endgame is rounding up the "creative" tier item from nearly every major mod in the pack in one final wave of quests.

If you're into modpacks that are hard but have a clear sense of cause and effect — instead of "do whatever, in whatever order" — this is the one.