Is this Hexblade 6th level ability replacement balanced?

Question

A frequent complaint with the Hexblade Warlock is that its 6th level ability Arcused Specter feels out of place. All of the other Hexblade abilities revolve around the Hexblade's Curse and single target damage; Accursed Specter, by contrast, is totally disconnected from Hexblade's Curse and provides a "pet" that does nothing to fit the Hexblade Warlock's theme of "enhancing oneself at the expense of another". What's more, adventures rarely face humanoid adversaries at higher levels, meaning that the Hexblade Warlock is often forced to forgo using the ability if they wish to avoid wanton murder.

In the following replacement ability, I've tried to keep the theme of exploiting a death, while connecting it to the subclass's core themes and Hexblade's Curse ability.

Capture Soul

At 6th level, when the target of your Hexblade Curse dies, you can use your reaction to capture the target's soul as if you had cast the spell Soul Cage with the following modifications:

• The spell affects creatures of any type except undead and constructs.
• The soul can be only be exploited a number of times equal to half your proficiency modifier, rounded down. Once used, you can't use this ability until you finish a long rest.

This ability functions as a significantly weakened version of Soul Cage, allowing only 1-3 uses, compared to the normal 6. It has the bonus of being able to be used on any target, a direct improvement to Accursed Specter, but requires a reaction and that the target be affected by Hexblade's Curse.

Overall, compared to Accursed Specter, this spell has much less combat utility but much higher out-of-combat utility, and scales better at higher levels. I like this ability because it gives the Hexblade something they can use for storytelling utility, rather than pure damage.

Is this balanced with respects to the original ability and the rest of the Warlock subclasses?

Answer 1

This is not overpowered

Accursed Specter is roughly comparable to the 6th-level spell create undead. Create undead allows you to make three CR 1 creatures instead of one, but Accursed Specter adds some extra buffs to your specter, the end result being that Accursed Specter is a bit weaker than a 6th-level spell.

Your feature, Capture Soul, also allows for a weaker version of a 6th-level spell, that spell being soul cage. Swapping spells of equivalent level is generally fine, as long as you understand that swapping a utility spell for a combat spell is liekly to be overpowered, and swapping a combat spell for a utility spell is likely to be underpowered.

You'd be fine allowing them to cast soul cage normally

Given the above, you're edging more on the underpowered side. And soul cage itself is a weaker spell even in term of utility, compared to 6th-level utility giants like mass suggestion and programmed illusion. Casting soul cage normally (but maybe without the any type buff) would still be balanced here.