There are three good reasons to forge the magical crystal chunks:
- Time. The most important reason, the crystal chunks allow you to save time on farming crystals.
- Bypass The Crafting Limit. Normally you can’t craft more than the equivalent of 30 Mystic Enhancement Ore per day. Magical crystal chunks do not count towards that crafting limit.
- Spend Spare Resin. If you don’t plan on spending your resin for anything else (e.g. going to sleep after gaming), just spend the last of your resin on forging magical crystal chunks.
Considering how difficult it is and how much time is needed to gather and process 120 Crystal Chunks for 15 minutes (the equivalent of 12 magical crystal chunks + 40 resin + 6 seconds), and considering that the magical crystal chunks also gives companionship EXP (up to 40 in this example), I’d say that while you might get better things for your resin from boss fights thanks to artifacts and ascension materials, it’s not so bad a deal over all… if you’re not a live streamer or someone who plays Genshin Impact all day.