This magic item refers to rules from the D&D 5th edition Basic Rules available here for free.
This sword was forged long ago by a Dwarven warrior who had an intense hatred for magic and wizards. Lore says that the last time the sword was seen was in the hands of a Dwarven Warlord named Terr’wobee who entered Undermountain and was never seen again. The sword attunes to its new master after being worn or carried for 24 hours. Before this time, the sword functions as simply as a +3 sword that does x3 damage against any humanoid with the Spellcasting ability.. Afterwards, however, the sword bestows the ability to Detect Magic () as long as the user is touching the pommel of the sword. Also, once per day, the user of the sword may use an Action to point the blade at a target and release a 20-foot cone-shaped burst of raw anti-magical energy that does 4d6 damage. (DC 14 Dex Saving Throw for 1/2 damage.) Lastly, as a Reaction, the user may use Counterspell as an ability three times a day. The user must be touching the grip of the sword and be able to see the spell being cast within the normal 60 feet. Daily abilities recharge at midnight as long as the sword remains in contact with the user.