Frozen Tooth of Azhaq (Patreon)

Greatsword, very-rare (requires attunement)

This greatsword is made from magic ice from an ancient silver dragon breath, it can’t be broken or melted. You gain a +2 bonus to attack and damage rolls made with this magic weapon. This greatsword has 6 charges and regains 1d6 charges every day at dawn. When you hit a creature with a melee weapon attack using this greatsword you can choose to expend up to 6 charges.

The attack deals an extra 1d8 cold damage to the target for each charge spent. Additionally, the target must succeed on a DC16 constitution Saving Throw or become restrained in ice for 1 minute. The creature can use its action to make a DC16 Strenght Saving Throw to break the Ice. On a success, it frees itself.

The sword regains 1 charge whenever you roll a natural 20 on an attack roll. It can’t hold more than 6 charges at the same time.