Hyperion Voyages uses a number of variant systems (some of which are heavily inspired by other sources) that are pervasive to this campaign setting and should not be removed. Exceptions and clarifications to each imported variant are written into their descriptions to fit in with rebalancing and so that they mesh well with eachother and the setting.
The GM must be willing to adapt their gamemastering style to the cold hard reality of how caster-archetypes work in D&D 3.5e.
First, your world must recognize that caster-archetypes (magic, psionic, or otherwise) are dangerous much like someone with a concealed and loaded military-grade automatic assault rifle is dangerous in the real world. They could be anywhere, and in some cases they can’t be truly disarmed. NPCs should generally feel uneasy around caster-archetypes, and even podunk local law enforcement should have caster-archetypes in their equivalent of SWAT teams and patrol squads. Every NPC must have grown up knowing that if you’re fighting a group, take out the caster-archetype’s first and as quickly as possible, preferably before the casters can unload their first volley. NPCs must use line-of-effect and line-of-sight to their advantage in the same way that having cover matters in modern first-person shooter games. Access to caster-archetype classes may be restricted and monitored by law in the same way that mutants were “registered” in the X-Men franchise.
Second, your quests must be designed to give the party a sense of urgency in their task, or everything you as GM do to balance the game will be for naught. The largest design flaw in D&D 3.5e is a concept called the “15-minute work day”. Many RPG groups run their party until the caster-archetypes drain their metaphorical batteries (which takes roughly 15 minutes of work in “game time”) and then they all stop and sleep for the “night”. This would have terrible in-game implications, as in reality everyone (especially the villain) has a timetable of plans that they’re working to bring to fruition as soon as possible. They won’t screw around, and neither should the PCs. You must — through quest design — force the prepared-type casters to feel like they have to leave spell slots open (decreasing how many spells are at their immediate disposal, which is key to balancing the system) or otherwise potentially become essentially-useless later on.
These variants apply to everyday adventuring and are the bulk of what makes this game feel the way it does.
Character Building Variants
Characters are built a little differently here.
All things non-mundane have had a major overall.
It is highly recommended that you use certain house rules when playing with this setting.