Sentient Echoes

An Echo can be given sentience, provided the one performing Resonance has a compatible spirit they can bond with the Echo.
In exchange for ten Chromatite Slabs, the item gains sentience and if it doesn’t already have it, the attunement property (this increases the item’s Frequency by 8). Use the “Creating Sentient Items” guide from the DMG (https://www.dndbeyond.com/sources/dmg/sentient-magic-items-artifacts#CreatingSentientMagicItems) to create the item as you would an NPC, rolling randomly to determine its traits and characteristics. At any time, you may spend an additional ten Chromatite Slabs to adjust one of the item’s sentient characteristics to a trait of your choosing.
Alternatively, you may spend the same Chromatites to bind a willing creature to the Echo. The creature loses its physical body in addition to any traits it can no longer use as a result of losing its body, but the Echo gains its Intelligence, Wisdom, and Charisma scores, in addition to the ability to speak any of the languages it knew in life. If the creature was capable of casting spells in life, it is still able to do so on your behalf, using its own resources and concentration in your stead. You cannot modify the creature’s characteristics.
A sentient Echo is under no obligation to be loyal to you, especially if its personal interests run counter to your own. For example, if you trick a devil into inhabiting your sword, and you have no interest in pursuing devilish ventures yourself, it may choose to try and manipulate circumstances to the best of its abilities to get revenge on you or even attempt to seek its own reincarnation (and subsequent escape from servitude).
Even still, sentient Echoes are otherwise treated as NPCs under your control. Naturally, Chromatian Staff reserve the right to point out when your Echo appears to be behaving uncharacteristically and will enforce meta gaming rules if you appear to be abusing this privilege. Don’t be a dick.