The following is the gameplay effects of choosing for a cleric in Aelsif any of the sects of Marakiziyy Monotheism. The fluff stuff is
here . These are up for review, though since this is not for D&D but rather a proprietary system it's less about balance and more about how fun or not they'd be to play. Unfortunately, as I started with the most vicious religion in the setting, those who enjoy kinder and more lighthearted characters would really have their work cut out for them trying to make one with these.
Fair warning: Aelsif is dark and full of terrors.
Element:
Some spells deal "deity's element" as their damage type. Other spells are only available if your deity is the right element, which obviously use that element in some capacity. IE, a fire-element deity like Yajvan (ALL of these below will be fire) only gets offensive spells that deal fire damage or fire and another element such as fire/electric. Their non-damaging spells are not affected much by element.
Favoured Weapons:
Some spells only work with your favoured weapons, such as Holy Weapon (which causes your deity's favoured weapons to do extra damage of the type of your deity's element). Some favoured weapons have (throw) listed on them, meaning you can get full effect throwing them, and they still count if launched by a thrower (such as a sling). Priests also have a power for each of their favoured weapons.
Additionally, clerics get holy flashsword spells for their favoured weapon that deal their deity's damage type. These spells can create any of their three favoured weapons out of their deity's element, lasting for one attack. Weapons designated (throw) are thrown instead of being used for a melee attack, which provokes an attack of opportunity, but otherwise this is a melee attack that does not provoke an attack of opportunity. The attack deals both a small amount of physical damage (which your physical stats do increase) but a large amount of elemental damage and can critically hit, though the elemental damage is not multiplied by the critical.
Notably, all four dedicated casters have flashsword spells, but this is far more restrictive than a mage's flashsword, which can only be a single weapon chosen at the time of preparation but can deal any damage type at the time of casting, or a shaman's flashsword, where each element is a separate spell but it's otherwise like the mage's, or a psion's flashsword, which is a weaker version of the mage's flashsword that is a cheap power instead of a spell and can be spammed at full attack rate. The restrictiveness of the cleric's flashsword is unique and makes it quite likely the worst version of the flashsword.
Domains:
Only matters to priests. You get one free cast daily of each spell level, which is selected ahead of time, and the spells you have to choose from are based on your deity's domain. For example, the greater spell (4th level out of 5) in Yajvan's unique Torture domain is "Circle of Despair", a minute-long aura buff that causes enemies that move near the caster to take a large debuff. Notably, you only get your domain spell for a spell level the class level after getting it. For example, you get minor spells at 1st level but your minor domain spells at 2nd level.
Powers:
Only matters to priests. This an elective list. You get electives at 4th, 8th, 12th, 16th and 20th level. Each sect below (and individual deity in polytheistic religions) only gets five powers, so you'll get them all by the time you max out your priest class.
Element: Fire
Favoured Weapons: Straight sword, mace, stone (throw)
Domains: Fear, war, death, destruction, torture.
Powers: Divine Retribution, Mace of Judgement, Cast the First Stone, Hellfire, God Fearing
Fear domain: Doom, circle of fear, terror, phantasmal killer, weird
War domain: Warrior's prayer, circle of valour, holy weapon, holy might, divine wind.
Death domain: Minor harm, lesser harm, harm, greater harm, major harm.
Destruction domain: Tremor, heavenly thunder, sunstrike, storm of vengeance, earthquake.
Torture domain: Minor curse, crushing despair, curse, circle of despair, major curse.
Divine Retribution: Your straight sword deals maximised damage against enemies that have hit you since your last turn.
Mace of Judgement: Striking other clerics with your mace burns them, causing an application of fire damage equal to your mace's damage dice plus your faith modifier.
Cast the First Stone: Any creature struck with a stone you have thrown or slung becomes shaken for one minute. A successful save grants immunity for 24 hours.
Hellfire: Any creature you deal fire damage to becomes shaken for one minute. A successful save grants immunity for 24 hours.
God Fearing: +4 to saves against fear.
Orthodox priests are built around fear effects. Using any two fear effects from Cast the First Stone, Hellfire and their list of fear spells will allow them to reach the higher of Aelsif's two stages of fear, terror, which causes enemies to try and flee (though they will still fight if cornered). Combining Hellfire and Mace of Judgement allows them to use a melee weapon to deliver fear, if only to other clerics, in addition to dealing high damage. Being resistant to fear effects and getting to retaliate very effectively with their sword are also nice touches.
Element: Fire
Favoured Weapons: Scimitar, whip, stone (throw)
Domains: Fear, compulsion, war, destruction, torture.
Powers: Smite the Necks, Obey Your Masters, Cast the First Stone, God Fearing, Jealous God
Fear domain: Doom, circle of fear, terror, phantasmal killer, weird
Compulsion domain: Charm, command, mass charm, mass command, dominate.
War domain: Warrior's prayer, circle of valour, holy weapon, holy might, divine wind.
Destruction domain: Tremor, heavenly thunder, sunstrike, storm of vengeance, earthquake.
Torture domain: Minor curse, crushing despair, curse, circle of despair, major curse.
Smite the Necks: Your scimitar's critical hits deal 3x damage instead of 2x.
Obey Your Masters: A creature struck with your whip gets a -2 to saves against compulsion effects for one minute.
Cast the First Stone: Any creature struck with a stone you have thrown or slung becomes shaken for one minute. A successful save grants immunity for 24 hours.
God Fearing: +4 to saves against fear.
Jealous God: You deal maximised fire damage to other clerics.
Revelant priests are more general-purpose than orthodox ones. They're a bit less capable of the fear-comboing, though they can still do it, but do better with compulsion and slightly better with melee attacks.
Element: Fire
Favoured Weapons: Straight sword, light shield, stone (throw)
Domains: Fear, compulsion, destruction, healing, wellness.
Powers: Divine Retribution, Divine Protection, Cast the First Stone, God Fearing, Curing Communion
Fear domain: Doom, circle of fear, terror, phantasmal killer, weird
Compulsion domain: Charm, command, mass charm, mass command, dominate.
Destruction domain: Tremor, heavenly thunder, sunstrike, storm of vengeance, earthquake.
Healing domain: Minor heal, lesser heal, heal, greater heal, major heal
Wellness domain: Minor antidote, lesser cure, antidote, greater cure, major antidote
Divine Retribution: Your straight sword deals maximised damage against enemies that have hit you since your last turn.
Divine Protection: When actively defending against an enemy using a light shield, the enemy you are defending against gets a -2 modifier to their damage roll.
Cast the First Stone: Any creature struck with a stone you have thrown or slung becomes shaken for one minute. A successful save grants immunity for 24 hours.
God Fearing: +4 to saves against fear.
Curing Communion: Drinking a serving of wine will allow a cure attempt on a single disease or poison effect, this attempt requires one minute of concentration. You gain a bonus on your cure roll equal to 1/2 your level of intoxication. You may only make one attempt per effect, per day.
Reformist priests are far more generalised than other monotheistic priests. Divine protection is a nice effect, it can't reduce an enemy's damage to 0 by itself, but it can if combined with DR or ER. Additionally, if the enemy you're defending against hits you (whether they deal damage or not) your counter attacks will be especially lethal.
Element: Fire
Favoured Weapons: Mace, flagellant's whip, stone (throw)
Domains: Fear, compulsion, death, destruction, torture.
Powers: Mace of Judgement, Mortification of the Flesh, Cast the First Stone, Hellfire, God Fearing
Fear domain: Doom, circle of fear, terror, phantasmal killer, weird
Compulsion domain: Charm, command, mass charm, mass command, dominate.
Death domain: Minor harm, lesser harm, harm, greater harm, major harm.
Destruction domain: Tremor, heavenly thunder, sunstrike, storm of vengeance, earthquake.
Torture domain: Minor curse, crushing despair, curse, circle of despair, major curse.
Mace of Judgement: Striking other clerics with your mace burns them, causing an application of fire damage equal to your mace's damage dice plus your faith modifier.
Mortification of the Flesh: Dealing unmitigated damage to yourself with a flagellant's whip allows you to make a single cure attempt against a poison or disease effect, this attempt requires one minute of concentration. You gain a bonus to your cure roll equal to the damage dealt. You may only make one attempt per effect, per day.
Cast the First Stone: Any creature struck with a stone you have thrown or slung becomes shaken for one minute. A successful save grants immunity for 24 hours.
Hellfire: Any creature you deal fire damage to becomes shaken for one minute. A successful save grants immunity for 24 hours.
God Fearing: +4 to saves against fear.
Prophetic priests are a good alternative to orthodox priests for fear, having the same powers used for it. However, Mortification of the Flesh gives a solid cure option as well, in exchange for them not being quite as combat-ready. The addition of the compulsion domain in exchange for losing war domain cements this, making it clear that prophetic priests are not meant to be as combat-oriented and more of a support priest. That does not, however, mean you should underestimate a prophetic priest in battle, especially if you yourself are a cleric.