An armblade is a magic weapon that attaches to your arm, becoming inseparable from you as long as you're attuned to it. To attune to this item, you must hold it against your forearm for the entire attunement period.
As a bonus action, you can retract the armblade into your forearm or extend it from there. While it is extended, you can use the weapon as if you were holding it, and you can't use that hand for other purposes.
A Lance requires two hands to wield when you aren't mounted.
You have Disadvantage on attack rolls with a Heavy weapon if it's a Melee weapon and your Strength score isn't at least 13 or if it's a Ranged weapon and your Dexterity score isn't at least 13.
A Reach weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for Opportunity Attack with it.
A Two-Handed weapon requires two hands when you attack with it.
If you hit a creature with this weapon, you can force the creature to make a Constitution saving throw (DC 8 plus the ability modifier used to make the attack roll and your Proficiency). On a failed save, the creature has the Prone condition.