Known by many names: the Sword of Seals, the Spiritblade, and Solon's Final Answer being some of the more well known. Nyssasbane was forged by the now Dead God of Dominion - Solon in order to Seal the Goddess of Dragons - Nyssa. This was the final battle in the Havensfall and considered the ending of that event. The sword is made of Mithral, this is most noticable at the blade, as the Crossguard and Handle are wrapped in fine black silk. The Crossguard has two colored diamonds embedded at each end, a Purple one on the left and a Yellow one on the right. A third colorless diamond is embedded at the end of the Pommel.
Unattuned, this blade has a +3 bonus to attack and damage rolls. If held for a minute by any intelligent creature, the spirits held in the diamonds begin to speak to the creature. The yellow diamond holds the spirit of the last Ruler of the Halflings, Caeser Atlas, who sacrificed his life to help Solon seal Nyssa. The purple diamond holds the spirit of the first Ruler of Sorab, Prince Haren, whose spirit was moved into the diamond to assist in resealing Nyssa. Atlas and Haren often argue with eachother, Atlas prefering Lawful actions and Haren prefering Chaotic actions, both spirits are Good Aligned though and dispise needless killing and destruction. This blade can not be attuned to without the permission of both spirits.
An Attuned Creature gains the following:

Your Armor Class increases by 1 as your skin grows purple scales. The purple scales can easily be hidden underneath any clothing.
You gain Resistance to Force Damage.
You are Immune to the Frightened Condition.
This Weapon deals Force Damage to any Ethereal Creature and ignores any chance to miss because of Etherealness, such as Blink.

If you would kill a Creature from an Attack with this Weapon, and that Creature is an Outsider (not from the Material Plane), an Undead, Composed of Energy, Created by Energy (such as a Skeleton or an Animated Armor), or in rare cases a Deity, you can activate the bottom sealing diamond. Doing so seals the Creature's Spirit; in the case of a Composed of or Created by Energy Creature, the Magicial Energy. If the Spirit sealed is an Outsider can be sent back to their Native Plane by casting Banishment on the diamond, or destoryed by removing the diamond and using a Wish Spell to destroy the diamond and the Creature. If the Spirit sealed is an Undead the Spirit can be sent to the afterlife by immersing the diamond in Holy Water for 1 Hour. If a Magical Energy was sealed you can use an Action to fire the Magic 30ft away as an Attack, if it hits it deals 1d12 Damage plus an additional die per every 2 CR of the former creature, the damage is based on the Magic (such as Necrotic for a Skeleton).
If the creature has a CR of 20 or higher they can make a Charisma Save DC25 (no Legendary Resistance or Rerolls) every day to attempt escape. The Creature must make three successful attempts in order to escape, a Natural 20 counts as two successes and a Natural 1 Removes one success.

Gaining the loyalty or trust of Atlas and Haren gives additional effects.
If you gain the loyalty or trust of Atlas you gain a Natural Luck. When you roll a d20 for any reason, you may activate your Natural Luck to reroll the d20, you must choose to do so before the DM tells you if you succeeded or failed. You must use the new roll even if it is lower. After you use this Natural Luck, you can't use it again until you complete a Short or Long Rest.
If you gain the loyalty or trust of Haren you gain a Breath Weapon. You can use your action to exhale destructive energy. When you use your Breath Weapon, each creature in a 15ft Cone must make a Dexterity Saving Throw. The DC for this Saving Throw equals [8 + your Constitution Modifier + your Proficiency Bonus]. A creature takes 5d6 Force Damage on a failed save, and half as much damage on a successful one. After you use this Breath Weapon, you can't use it again until you complete a Short or Long Rest.

This is the sealing place of Nyssa Goddess of Dragons and its powers are directly related to the fact that Nyssa is sealed within. The amulet is made of a dark grey Cold Iron with a colorless diamond set in the center. If held for a minute by any intelligent creature the spirit of Nyssa held in the diamond begins to speak to the creature. Nyssa desires to be released from the Godprison and will attempt to direct an Attuned Creature to search out things that could potentially release her, through Persuasion, Bribes, Seduction, Intimidation, Deception, Dreams in the creature's Sleep, or any method that Nyssa believes to be the most likely to work.
A creature wearing the Amulet gains the following:

The amulet can be used as Spell Focus for any Class that can use one to cast Spells and you can do so even while both hands are occupied.
Your Armor Class increases by 1 as your skin grows mercury scales. The mercury scales can easily be hidden underneath any clothing.
You gain Advantage to any Save versus any Prismatic Effect, such as Prismatic Spray. In addition if you succeed the Save, you ignore all effects.
You are Immune to the Frightened Condition.
If a Dragon attempts to use its Frightful Presence against you, you are immune and the Dragon must immediately Roll a Save against its own Frightful Presence.
Twice per Day you can use an Action to regain a 5th-Level Spell or lower.
Once per Day you can use an Action to cast Prismatic Spray. You cast the Spell from your mouth as a Breath Weapon. This does not use Spell Slots and the creature does not have to know Prismatic Spray or even be a Spellcaster to do this.