I'm pretty sure I fixed the map problem - check it and let me know if you see it now.
The world is 100% homebrew. I'm also open to player input for setting details that I haven't already established. We'll see what comes up as we play; I don't want to overwhelm people right off the bat, and it's probably better that I don't put much more energy than I already have into defining bits that will never actually come up in the campaign.
Once other players join in we'll see what they say about different activities, but one comment on what you've suggested so far is that I would definitely be on board with your "base building" idea. I haven't put much thought yet into specific cults/guilds/etc, so this might be a fun way to play around with that aspect of the game.
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There are five types of magic in Mythras, each with distinct mechanics and spells (this is one of the things that got me excited about this system as I was reading it).
- Folk Magic - the simplest form of magic, and the one that is described in the "Magic" section of the quick start rules. Requires the Folk Magic skill to cast spells, and each spell costs 1MP. All Folk Magic spells are fairly weak for purposes of interacting with other magic, e.g. bypassing someone else's protection spell. Sample spells include Bladesharp (increase the damage die of a bladed weapon), Disruption (deal 1d3 damage to an object or animal), and Voice (the speaker's voice is amplified such that everyone in range is forced to listen).
- Animism - deals with spirits - at low levels it's just detecting and maybe communicating with them, at higher levels you can negotiate or coerce them, and also project yourself into the spirit world. Requires the Trance and Binding skills. Rather than learning spells, the animist develops relationships with various spirits (or compels them into service), and then gets the spirits to use their supernatural abilities. MP cost depends on how powerful the spirit is and what you want it to do. Examples include ancestor spirits, elemental spirits, and wraiths.
- Mysticism - intense focus that gives the caster (and only the caster) a variety of supernatural buffs. Requires the Meditation and Mysticism skills. MP cost depends on the type and magnitude of effect, but will usually be in the 1-6 range. Many spells give you a bonus to a particular skill or attribute, but others include enhancements such as Arrowcut (ability to parry missile weapons with your hands or melee weapon), Immunity (total immunity to a specific source of damage), and Pain Control (automatically succeed at Endurance rolls against injuries).
- Sorcery - the traditional "read an arcane tome and learn to manipulate the laws of the universe" style of magic. Requires the Invocation and Shaping skills. In addition to simply casting spells, it also lets you modify certain attributes such as the duration or number of targets, and even combine multiple spells into a single casting. MP cost starts at 1 per spell and increases depending on how many modifications you make. Sample spells include Castback (spells targeting the sorcerer have a chance of bouncing back to the caster instead), Fly (lets you fly), and Wrack (the all-purpose damage-dealing spell, which gets reskinned with fire or acid or flying blades or whatever as suits your particular school).
- Theism - magic granted by a deity. Requires the Devotion and Exhort skills. Magic points must be banked ahead of time by prayer or other acts of devotion, which can only be done at a temple or other holy site, but you can cast spells any time once the points are there. Spells cost 1-3 MP depending on the power level. Sample spells include Awaken (bring the deity's awareness and control into a sacred statue or animal), Earthquake (ranging in power from minor inconvenience to bringing down mountains), and Steadfast (all people within the area of effect are immune to mental or emotional manipulation).
Learning a new spell costs 3xp for folk magic, and 5xp for mysticism, sorcery, or theism, and in any case requires that you have access to the new spell. For animism it depends on the specific spirit you are trying to bind or negotiate with.
For all types of magic, which spells are available depends on the source you learn it from. For example, a particular spirit cult will be allied with certain types of spirits and hostile to other types, and a particular school of sorcery or mysticism will only teach the spells which align with the philosophy of that school. There is no "universal" spell list from which to pick and choose like you get in D&D. It is possible to learn spells from outside of your tradition, but it takes considerable in-game effort.