Ghostly

New mobs:

• Darkness Mage (300 health, half corporeal so acts like it has 600 unless you have Corporeality tools)
• Shadow Remnant (1 health, but shrinks instead of its health going down - summoned by Darkness Mages and should occur if a Possessed Undead dies, chance configurable)
• Sickened Spider (10 health, 10% smaller than a normal spider, may be slower than a normal spider and is only half corporeal, so unless you have Corporeality tools it acts like it has 20)

New Corporeality toolset:

• Sword of Corporeality
• Axe of Corporeality
• Bow of Corporeality
• Venombow of Corporeality
• Pickaxe of Corporeality
• Shovel of Corporeality
• Hoe of Corporeality

New arrow:

• Dusted Arrow of Corporeality

New bow:

• Venombow

New items, excluding tools:

• Corporealite Ingot
• Corporealite Nugget
• Darkness Mage Flesh
• Venomstring

New blocks:

• Corporealite Ore (generates in the Nether)
• Block of Corporealite

New advancements:

• Ghostly (root for Ghostly advancements tab, immediately granted if you don't have it)
• Evil Spirits, Beware (obtain a Bow of Corporeality)
• Ranged and Venemous (obtain a Venombow)
• Isn't it Pickaxe of Corporeality (obtain a Pickaxe of Corporeality)
• Acquire Corporealware (obtain a Corporealite Ingot)
• What's This? (obtain a block of Corporealite Ore)
• The Spirits Dislike You (be killed by any Possessed Undead, or a Shade)
• You've Angered the Spirits (be killed by all Possessed Undead, and a Shade)
• Spirit Vanquisher (kill any Possessed Undead, or a Shade)
• Spirits Vanquished (kill all Possessed Undead, and a Shade)

New rarities:

• Corporeal (gold)
• Shadow (dark gray)
• Venom (dark green)

Some items have additional lines of information in their inventory tooltip, displayed when you hover over the item with your cursor in an inventory (your own, chest, furnace, crafting table, etc., though technically crafting tables don't have an inventory due to not storing items)

For resource pack makers, data pack makers or translators: All advancements are changeable and disableable, in addition to their titles and descriptions translatable, and all item tooltips can be translated - see the mod's en_us.lang file to see the names used for tooltip lines and advancement titles and descriptions. However, colors are hardcoded to be the same as the items' rarities. For a guide on data packs and changing advancements, see https://minecraft.gamepedia.com/Data_pack (you'll need to make a new data pack and, rather than using minecraft for the domain name, use ghostly). Due to data packs, mob loot tables can also be overriden or disabled, though if you disable them via making them invalid you will get log errors. Same goes for advancements.