This is too strong

We could go into detailed analysis, but I think this is too strong based just on Demonic Regeneration alone. The Ring of Regeneration, which is already very rare, just one step from legendary, regenerates 1d6 hits or on average 3.5 per 10 minutes, or 0.35 per minute or 0.035 per round. The also legendary Ioun Stone of Regeneration gets you 15 hits at the end of each hour, or 0.025 points per round. This thing regenerates Charisma modifier hit points per round, and we can assume that modifier is +6 for a level 15 Warlock due to the Abyssal Presence bonus. That is 171 times the amount being regenerated by the ring. Even for a legendary item, that seems beyond the pale.

On top of this, the thing provides a +2 bonus to your main stat, Charisma, worded in a way that I think is meant to get around the cap of 20 Charisma limtiation, as it adds a bonus, it does not increase the stat. Again that in itself is already better than a very rare Ioun stone of Leadership, because there are few ways to get beyond 20. It reinforces all your primary spell attacks, spell save DCs etc. It is even better than a Tome of Leadership and Influence, that increases your stat and maximum score, because there is a hard ceiling to the maximum for gods and the like at 30, and this could get around that.

The AC bonus, skill advantages and in-combat reslilience switch are than just heaping more on top. The latter effectively is close to resistance against all damage types except magical weapons, which is also huge, especially in combo with the regeneration.

This is too strong

We could go into detailed analysis, but I think this is too strong based just on Demonic Regeneration alone. The Ring of Regeneration, which is already very rare, just one step from legendary, regenerates 1d6 hits or on average 3.5 per 10 minutes, or 0.35 per minute or 0.035 per round. The legendary Ioun Stone of Regeneration gets you 15 hits at the end of each hour, or 0.025 points per round. The Abyssal Regalia regenerate Charisma modifier hit points per round, and we can assume that modifier is +6 for a level 15 Warlock due to the Abyssal Presence bonus. That is 171 times the amount being regenerated by the ring. Even for a legendary item, that seems beyond the pale.

On top of this, the Abyssal Regalia provide a +2 bonus to your main stat, Charisma, worded in a way that I think is meant to get around the cap of 20 Charisma limtiation, as it adds a bonus, it does not increase the stat. Again that in itself is already better than a very rare Ioun stone of Leadership, because there are few ways to get beyond 20. It reinforces all your primary spell attacks, spell save DCs etc. It is even better than a Tome of Leadership and Influence, that increases your stat and maximum score, because there is a hard ceiling to the maximum for gods and the like at 30, and this could get around that.

The AC bonus, skill advantages and in-combat reslilience switch are than just heaping more on top. The latter effectively is close to resistance against all damage types except magical weapons, which is also huge, especially in combo with the regeneration.

This is too strong

We could go into detailed analysis, but I think this is too strong based just on Demonic Regeneration alone. The Ring of Regeneration, which is already very rare, just one step from legendary, regenerates 1d6 hits or on average 3.5 per 10 minutes, or 0.35 per minute or 0.035 per round. The also legendary Ioun Stone of Regeneration gets you 15 hits at the end of each hour, or 0.025 points per round. This thing regenerates Charisma modifier hit points per round, and we can assume that modifier is +6 for a level 15 Warlock due to the Abyssal Presence bonus. That is 171 times the amount being regenerated by the ring. Even for a legendary item, that seems beyond the pale.

On top of this, the thing provides a +2 bonus to your main stat, Charisma, worded in a way that I think is meant to get around the cap of 20 Charisma limtiation, as it adds a bonus, it does not increase the stat. Again that in itself is already better than a very rare Ioun stone of Leadership, because there are few ways to get beyond 20. It reinforces all your primary spell attacks, spell save DCs etc. It is even better than a Tome of Leadership and Influence, that increases your stat and maximum score, because there is a hard ceiling to the maximum for gods and the like at 30, and this could get around that.

The AC bonus, skill advantages and in-combat reslilience switch are than just heaping more on top. The latter effectively is close to resistance against all damage types except magical weapons, which is also huge, especially in combo with the regeneration.

This is too strong

We could go into detailed analysis, but I think this is too strong based just on Demonic Regeneration alone. The Ring of Regeneration, which is already very rare, just one step from legendary, regenerates 1d6 hits or on average 3.5 per 10 minutes, or 0.35 per minute or 0.035 per round. The also legendary Ioun Stone of Regeneration gets you 15 hits at the end of each hour, or 0.025 points per round. This thing regenerates Charisma modifier hit points per round, and we can assume that modifier is +6 for a level 15 Warlock due to the Abyssal Presence bonus. That is 171 times the amount being regenerated by the ring. Even for a legendary item, that seems beyond the pale.

On top of this, the thing provides a +2 bonus to your main stat, Charisma, worded in a way that I think is meant to get around the cap of 20 Charisma limtiation, as it adds a bonus, it does not increase the stat. Again that in itself is already better than a very rare Ioun stone of Leadership, because there are few ways to get beyond 20. It reinforces all your primary spell attacks, spell save DCs etc. It is even better than a Tome of Leadership and Influence, that increases your stat and maximum score, because there is a hard ceiling to the maximum for gods and the like at 30, and this could get around that.

The AC bonus, skill advantages and in-combat reslilience switch are than just heaping more on top. The latter effectively is close to resistance against all damage types except magical weapons, which is also huge, especially in combo with the regeneration.