Mod Iter RPG by AcmaKurihara

Ametrine

Magenta crystals with peculiar magical properties. Ametrine shards is an important material in the mod progression, especially for the mages. Generates underground in medium-sized deposits, both stone and deepslate variants. Can be mined with iron pickaxe tier and above. Ametrine shards can be crafted into a block.

Voidquartz

Dark crystals that grow in the darkest and deepest places of the overworld. Come in two sizes - one and two blocks tall. Very sturdy, drop voidquartz shards when mined with iron pickaxe or above.

Voidquartz shards are magically "hollow", which allows them to store and condensate mana, this property is used to create magical catalysts. Voidquartz shards also have a block version.

Magmanum

Condensed rage of now extinct demons, magmanum is a fiery red ore that is found in the Nether. Fueled by hate, it endlessly burns, which allows for it's easier location. When broken, magmanum ore releases it's vile spirit, performing a variety of chaotic actions, such as setting the player on fire, placing lava source or even exploding. Magmanum ore drops magmanum chunks that are used for demon-themed armor and weapon sets.

Geodes + geodite

Upon killing a mob in any of the 3 vanilla dimensions, a geode of respectful stone type has a slim chance to drop. Overworld has stone and deepslate geodes, nether has netherrack and blackstone geodes, end has only one geode. Geodes can be cracked open by right-clicking them with any pickaxe in the offhand, pickaxe has a change to lose durability, Unbreaking enchantment further decreases the chance.

Additionally, for each geode, there is a Geodite of it's type. Geodites are blocks, rock formations with geodes inside them. Geodites are extremely rare, and therefore valuable. Geodite block drops 4-8 geodes upon mining, but can be picked up with a silk touch enchanted pickaxe. By placing a Drill block (crafted with iron, obsidian, comparators and voidquartz block) below it, drill will start producing a single geode per minecraft day, indefinetely, thus making it a slow middle-game ore farm.

Mod adds 4 new melee weapon types for all vanilla materials and more.

Shortswords - double the speed, half the damage compared to swords.
Scythes - sweeping edge on steroids. Slow, deals less damage but has a large area of cover.

Spears - also slower and weaker, but partially ignores armor and protection enchants, good choice for pvp.

Flails - slow and strong, take forever to wind up but perform devastating hits.

5 elements of nature. Earth, Water, Air, Fire and Void.

Play may encounter elementals - embodiments of those natural powers all around the world. Earth elementals spawn in lush caves, Water elementals emerge from oceans and wander beaches, Air elementals glide through high skies and mountain peaks, Fire elementals are found in the Nether and Void elementals reside in the outer islands of End.
Each elemental is a tough encounter, every type has its own unique attacks. Earth elemental summons vines to tangle and prick the player, Water elemental launches exploding blobs of seawater, Air elemental forms a windswirl to toss the player away, Fire elemental shoots fireballs that set blocks on fire and additionally erupts into fountain of fireballs on death.

Elementals drop Elemental fragments of their type. Elemental fragments can be combined with ametrine ingots using corresponding rune to create elemental ingots, allowing armor and weapon sets to be crafted.

Earth element - Forest set:
Weapons create poisonous razorsharp leaves in an area
Armor allows you to pass through leaves when sneaking

Water element - Ocean set:

Weapons strike through hit target, launching a barrage of droplet projectiles behind it
Armor grants dolphin's grace and allows to replenish oxygen by sneaking on a block underwater

Air element - Sky set:
Weapons apply brief levitation to mobs in an area, shift-hits lauch struck entity away from you
Armor gives double jump ability and slow falling

Fire element - Hell set:
Weapons ignite mobs, if struck mob is on fire then deals additional damage and ignites some nearby mobs. Extremely weak against nether residents.
Armor allows you to perform dashes by sneaking in sprint. You deal damage, ignite and push mobs away from you when dashing.

Iter RPG adds a separate weapon type - magical. All magic weapons use mana in terraria-like fashion. By default, player is unable to generate and store mana, one needs a catalyst on the early stages of the game to do that. Catalysts are curio baubles that, when equipped, passively generate and store mana that the player can use. Each catalyst has different mana regen and capacity stats.

Arcane bouquete - your first catalyst, restores 0.03 mana per tick, caps at 12.

Ametrine geode - cluster of crystals made with arcane dust and ametrine, restores 0.05 mana per tick, caps at 16.

Possession - skull of a fallen wither skeleton, infused with mana. Restores 0.08 mana per tick, caps at 32.

In the Nether, a lonely grim steeple towers above the lava ocean... 
Sorrow Spire is a structure intended to be looted after clearing nether fortresses and before obtaining netherite. It is a stealth-based dungeon with mobs attacking you only if you disturb their peace. It generates at the lava sea level in any Nether biome.

Arthropod Catacombs dungeon is complete, will write about it later.

Carcasses are remnants of Nether's ancient overlords. Remnants of once powerful demons reanimated by their immortal souls. Carcasses roam the Nether Wastes, and will try to kill the player on sight. They still have a fraction of their demonic power that Carcasses can invoke. They can dash towards the player, cast a barrage of fireballs, summon bloody spines from the ground to impale it's enemies, call for lesser skeletons to aid and set blocks on fire.

On death, Carcasses' demonic soul is released to seek for a new body. Demonsoul looks for skeletons to posses, and turns them into Revenant upon attack. Revenants are faster and stronger skeletons that will try to kill the player at last. Revenants might also release a demonsoul, but the chance is lower. Revenants summon some demonspines on death.