Blast Disk

A blast disk holds destructive arcane power. A typical blast disk is about nine inches in diameter and one inch thick, made from layers of different metal; dragonshards are embedded in the surface of the disk and arcane symbols are engraved in its surface. Anyone studying the surface of the disk can make an Intelligence (Arcana) check corresponding to the save DC of the disk. On a success, they identify the spell effect contained within the disk. There are three elements to a blast disk: the trigger, payload, and charge. Each effect is selected at the time it is created.
Trigger. A spellcaster touching a blast disk can use an action to activate it. However, generally you don’t want to be holding a blast disk when it goes off. A blast disk can be created with one of the following triggers, or with a more complex trigger of the creator’s choosing (e.g. to detonate when a certain word is spoken, when a specific object comes within range, etc.):

• Time. When the disk is activated, the user can set a time delay of up to 10 minutes before it releases its effect.
• Proximity. 30 seconds after the disk is activated, it can trigger when someone comes within a certain distance of the disk or when someone first makes contact with the disk, then breaks that contact.
• Impact. The activated disk can be set to detonate on impact, then used by throwing or dropping it. 

Payload. When the blast disk is triggered, it produces one of the following magical effects, chosen when it was manufactured:

• Explosive. This creates an explosion in a 20-foot radius centered on the disk. Each creature in the area must make a DC 13 Dexterity saving throw, taking 11 (2d10) damage on a failed save, or half as much damage on a successful one. An explosive blast disk deals triple damage to objects or structures. The damage type is set when the disk is created.
• Spell Effect. The disk produces a spell effect when triggered. The effect must target either a single creature—whoever triggers the disk—or an area of effect centered on the disk. The level of the spell in the disk determines the saving throw DC and attack bonus, as well as the item’s rarity, as shown on the Blast Disk Power table. 

Charge. A typical blast disk holds a single charge, the dragonshards shattering when the effect is triggered. However, more advanced blast disks recharge at dawn; this increases the rarity of the disk by one category. 
Disarming a Disk. When used on the battlefield, blast disks are typically buried or hidden. Finding the disk requires a successful Intelligence (Investigation) check, with a DC equal to the ability check that was used when it was hidden, such as Wisdom (Nature) or Dexterity (Sleight of Hand). To disarm a blast disk, a character with proficiency in Arcana must succeed on a Dexterity check using thieves’ tools, with a DC equal to the save DC of the disk. If the check is failed by 5 or more, the disk detonates as if it were triggered. Successfully disarming a blast disk expends one charge, meaning most blast disks will be rendered inert after disarming.