- The Red Gems are only to access the bonus dungeon, which doesn't really have anything it other than a tough boss fight. You need all 40, and if you already missed some there is absolutely no way to go back for them.
- Beyond that, just make sure you kill every enemy in the zone before moving on to get the most stat ups and explore thoroughly, some of the stages (Mu especially) are confusing as hell.
- Oh, and the bosses just get more and more annoying, the boss of the desert temple is especially bad if I recall. Oh, and both Soulblazer and Terranigma are much better games in my opinion, but IoG has a certain bizzare charm.
- Don't worry too much about getting every single stat-up for killing all the monsters. When you beat the boss of a stage the game will give you all the ones you missed.
- After you unlock the boss chamber (you'll know), it is possible to get Freedan for use against the bosses. You backtrack along the second level. His Dark Space is right after a row of six retracting spikes.
- I've always thought Mu was the most annoying area of the game. Its bosses are the most annoying of the game because they require that paying-attention-to-multiple projectiles skill you can only truly gain from vertical shoot-em-ups. But on the good side, it only has one Red Jewel and it's easy to find. Also, the rest of the game is pretty much clear sailing. There's a secret passage you have to find to advance in the Angel Village, but nothing too hard after that. I personally didn't think any of the following bosses were all that difficult.