Ok, here comes starter for the soul rules.<br/><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Acquire souls</div><div class="spoiler_body">Souls who die go to their respective planes/domains, evil souls go to lower planes and become new creatures. Mostly in form of maggot like creatures with barely recognizable face with fragment of mortal memories and minds enough for them able feel fear and despair. Easiest way to gain souls is by capturing these maggots and sacrificing them, however to gain anything from them you need hundreds and even thousands of them.<br/><br/>Soul energy is called <em>Incarnum</em> (https://vignette.wikia.nocookie.net/riftlore/images/7/79/The_Soulstream.png/revision/latest?cb=20130219171251). Some mortal beings are able use this energy in raw form and pull it from stream of souls which depart upon the planes. Outsiders bodies consist of such energy and are unable use incarnum with mortal's methods. But they can use it other means; to reinforce their existing incarnum, shape it and empower it.<br/><br/>The most potent sources of incarnum are living mortals sacrificed on dark rituals meant to bind their incarnum to respective outsider. In tradeable form incarnum takes form of glowing blue crystals, which size, shape and structure all are individual to given soul. There also can be spells which directly take souls from victims, if outsider performs it, it can transform soul into incarnum crystal.<br/><br/>The ratio how incarnum value is 4 x HD of soul sacrificed. So 1 HD human sacrificed counts as four unit incarnum energy. However brilliant and vibrant souls provide more; adventurers (PC classed) and any divine associated mortals (clerics and paladins example or anyone with divine spell slots) grant twice as much incarnum energy. When speaking of mortals, it means any living humanoid which can die of old age (including dragons). Dragons count ten times as much per HD in incarnum energy and are most potent.<br/><br/>Can you harvest incarnum from a living outsiders? Yes but it needs done slowly, slowly killing outsider via physical torture allows get 10 incarnum energy per HD (and torture takes 1 HD per day away). So it's not efficient and lost HD on outsider cannot be recovered by magic besides wish or miracle.</div></div><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Spend souls</div><div class="spoiler_body">Spending souls can be for three things; creating artifacts, add features to Archfiend's keep or empower yourself.<br/><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Artifacts</div><div class="spoiler_body">Artifacts are created much as any magic item but artifacts are indestructible (expect by specific method), cannot divined and besides base properties of existing item has unique power. You create firstly base item (pay x10 item's cost in incarnum energy + item's base cost in gp minus halving for crafting it or other benefits). Then you get create custom power on artifact. Artifacts are in two tiers; minor and major. It is simply scaled based on scope given artifact.<br/><br/>Minor (25,000 incarnum)<br/>= Any power which affects only the user itself or one another person or generates one specific thing in small scale.<br/><br/>Major (250,000 incarnum)<br/>= Any power which affects large area, generates enormous amount of something or has global effect (based on build up overtime).<br/><br/>GM decides/allows all given artifact powers and which tier they belong to.</div></div><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Castle Upragdes</div><div class="spoiler_body">You can sacrifice incarnum to give additional features to the castle itself, or upgrade existing feature further/more potent.<br/><br/>Upgrade existing feature: 10,000 x times upgraded in incarnum<br/>Add new feature: 100,000 incarnum<br/><br/>Feature given is given same way how archfiends gave shard of their own power into castle. But considering now incarnum is used, they can focus and give feature from a specific creature (which incarnum energy is used empower the castle), through using  focus (a body part, blood or other focus suitable to the task). Exact nature of potency or manifest of feature is decided/approved by GM.<br/></div></div><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Empower yourself</div><div class="spoiler_body">Archfiends can empower themselves with incarnum energy. These are following listed methods;<br/><br/>-Level up<br/>-Gain new Archfiend power (passive)<br/>-Gain new Archfiend power (special attack)<br/>-Upgrade existing power<br/>-Improve Ability Score<br/>-Gain new (additional) feat<br/><br/><strong>Level Up:</strong> Simply pay cost between present level and new level with incarnum energy.<br/><strong>Gain new Archfiend power (passive):</strong> Flat cost 100,000, then 100,000 x per purchase of this trait. Feature must come from creature of equal or less than your HD.<br/><strong>Gain new Archfiend power (special attack):</strong> Flat cost 250,000, then 250,000 x per purchase of this trait. Feature must come from creature of equal or less than your HD.<br/><strong>Upgrade existing power:</strong> Costs 50,000, then 100,000 and then 150,000. Max 3 times can be upgraded and same cost applies both passive and special attacks. Upgrade usually doubles a given factors or adds +5 to save DC.<br/><strong>Improve Ability Score:</strong> Incarnum cost is stat score (new value) x 100 in incarnum. So moving from 19 Int to 20 costs 2,000 incarnum. Moving to 21 after that costs 2,100.<br/><strong>Gain new (additional) feat:</strong> Costs 25,000 incarnum + 25,000 incarnum per prerequisite the feat has (other feats, BAB requirement, skill requirement etc, this cost stacks). Need still qualify to take the feat.<br/><br/>Additional power ups (like extra spell slots, new spell-alikes) can be added above list but for discussion sake I wrote the above and check opinion on it.<br/></div></div></div></div>