@Lava_雏莲 在“A Dictionary Of Alchemical Imagery”中找到了可能和"埃尔德里奇"相关的资料。
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【图1、2】
projection
the final operation of the opus alchymicum, when the *philosopher’s stone or tincture is thrown over the base metal to transmute it into silver or gold; the instant exaltation or *augmentation of a substance by the *medicine or philosopher’s stone. [...]
The emblem illustrating the projection in ‘Coronatio naturae’ (GU Ferguson MS 208) shows the red tincture projected from the heart of the *red king (the red stone) onto his subjects, who personify the base metals (fig. 32).
投影
炼金术的最后一项操作，将*贤者之石或酊剂投掷到贱金属上，将其转化为银或金；通过*药或贤者之石瞬间提升或*增强物质。[...]
“Coronatio naturae”（GU Ferguson MS 208）中描绘投影的徽章显示了从*红王（红石）心脏投射到其臣民身上的红色酊剂，这些臣民是贱金属的化身（图 32）。【图3】
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【图4、5】
purple tincture
the same as the red elixir or stone. The Latin purpureus-a-um means purple-coloured; dark red, dark brown. The *red stone or elixir, which can tinge all base metals to gold and restore man to perfect health and consciousness of God, is frequently described as the precious purple tincture. [...]
The colour of the tincture is frequently compared to the Tyrian purple of costly fabrics worn by persons of royal or imperial rank, and made from molluscs called (in Greek) porphura (see dye). [...]
One of the most frequently occurring images symbolizing the attainment of the purple tincture is that of the king putting on the purple robe. The purple robe and crown of the king as *red stone are illustrated in GU Ferguson MS 271 (fig. 33).
紫色酊剂
与红色万灵药或石头相同。拉丁语 purpureus-a-um 的意思是紫色；深红色，深棕色。红色石头或万灵药可以把所有贱金属染成金色，使人恢复完美的健康和对上帝的意识，经常被描述为珍贵的紫色酊剂。[...]
酊剂的颜色经常与推罗紫色相比较，推罗紫色是皇室或帝国级别人士所穿的昂贵织物的颜色，由一种称为（希腊语）porphura（见染料）的软体动物制成。[...]
象征获得紫色酊剂的最常见图像之一是国王穿上紫色长袍。GU Ferguson MS 271（图 33）中展示了国王的紫色长袍和红色石头王冠。【图6】
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投影的部分可能可以对应“贵化黄金乡的埃尔德里希尔”和”红色血染的埃尔德里希尔“。
紫色酊剂的部分在你写的“金棺材：【黄金国】卡组设计历史原型个人考据”中已经提到了，恰好这本书可以支持你的推论。推罗紫色染在布料上会显得红【图7】，所以古炼金术文可能会把红色紫色互换使用来形容这红紫色。
Magnum Opus的炼金过程在早期是4个阶段：
黑化：（拉丁语）nigredo、（希腊语）melanosis
白化：（拉丁语）albedo、（希腊语）leucosis
黄化：（拉丁语）citrinitas、（希腊语）xanthosis
红化：（拉丁语）rubedo、（希腊语）iosis
从”Splendor Solis，Plate III – The Second Treatise“的图画可以看见炼金的过程。骑士胸口上布置了炼金过程的4个颜色黑白黄红，骑士的左脚踩着的喷水池的汞水，到了骑士的右脚踩着的喷水池变成了金水。【图8】
到了15世纪之后有些炼金作者开始把黄化阶段压缩进红化阶段，把炼金过程剪成3个阶段。不过这炼金过程基本上很有争议。从阿拉伯、古埃及传到古希腊、古罗马，每个炼金作者都有自己的理解，所以各写各认为的炼金过程。比如”Amphitheatrum Sapientiae Aeternae Solius Verae“的炼金过程就如你个人考据中提到的采用了孔雀尾阶段（从下往上：黑化→白化→孔雀尾→红化）。【图9】
埃尔德里奇的配色方案可能是炼金过程的黑白黄红（紫）。
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参考：
[1] “A Dictionary Of Alchemical Imagery” by Lyndy Abraham
[2] "Imagens alquímicas renascentistas: um estudo preliminar do manuscrito La génération et opération du grand oeuvre pour faire de l or (1620)" by Reno Stagni
tede.pucsp.br/bitstream/handle/13401/1/Reno%20Stagni.pdf
[3] "Splendor Solis" by Solomon Trismosin
chymist.com/Splendor%20solis.pdf
[4] "Amphitheatrum Sapientiae Aeternae, Solius Verae" by Heinrich Khunrath
search.library.wisc.edu/digital/AH6PQ2FLXSD5FI8O
