Paizo has discontinued the use of the word "phylactery" in its Pathfinder publications due to the word's origins as an item used in real-world religious customs. In the most recent chapter of Strength of Thousands, Pathfinder 2E's current Adventure Path, Paizo noted that it would use the phrase "soul cages" to describe the physical item that a lich stores their soul in. Traditionally in Dungeons & Dragons, Pathfinder, and other fantasy tabletop games, the item was known as a phylactery.
In the table of contents to Doorway to the Red Star, Paizo explains their reasoning: "Starting with the lich Dwandek in this adventure, we're making a long‑overdue terminology change. The use of the word "phylactery" as the item in which a lich stores their soul is both inaccurate and inappropriate given the evil nature of liches and the word's connotation with real‑world religious practices. Instead, liches in Pathfinder Second Edition store their souls in objects called soul cages—an act that liches see as an ultimate act of defiance against the cycle of life and death. Liches consider their souls not as things to cherish, but as weaknesses that, once locked away in a cage, allow for eternal undeath. Apart from this change in name, the mechanics for how liches function remain unaltered."
Gary Gygax and Rob Kuntz introduced what modern fantasy fans recognize as the lich in the pages of Greyhawk, the first-ever rules expansion for Dungeons & Dragons. Their version of the lich (which to that point was used as a generic synonym for the undead) was that of an undead magic user who retained their abilities from beyond the grave. Gygax expanded upon the lore of the lich in the original Monster Manual, specifying that liches were magic-users who through foul sorcery had conquered death by placing their soul inside an arcane box. Gygax called this box a phylactery, a word also used to describe a leather box worn by some Jews while praying that contained passages of the Torah. Many Jews alternatively referred to a phylactery as a tefillin, and the word "phylactery" is associated with a tefillin through the Greek New Testament. It's noted that subsequent descriptions of the phylactery in Dungeons & Dragons even went as far as to note that the box contained spells written on strips of paper, similar to how a tefillin contains passages of the Torah inside of it.
Because liches are depicted almost universally as evil creatures in Dungeons & Dragons and other fantasy properties (some methods of becoming a lich involve the ritual sacrifice of an infant) and because the phylactery is usually depicted as an evil artifact, some have pointed out that using the word seems problematic. While the word phylactery has historically had other uses than as an item used in Jewish religious practices, at least some game designers have either consciously or unconsciously appropriated the tefillin when describing the item used to hold a lich's soul. Given how much Anti-Semitic imagery and symbolism crops up in fantasy literature either through ignorance or deliberate bigotry, Paizo's move seems reasonable and their new terminology makes a lot of practical sense.
We'll likely hear much more about soul cages, as Paizo plans to release Book of the Dead, a new rulebook covering the undead, next year.