Alter Foci
Alter Foci are items that were created to alter and/or improve frequently cast spells. Powerful though they are, most take at least a spell several steps in power above its base to be activated.
Handheld Launcher
Wondrous Item, Rare (Requires attunement by a spellcaster that knows Magic Missile)
This inscribed device is reminiscent of a pistol with a crystal instead of a drum or barrel. It has no apparent mechanism for firing its ammunition outside of a trigger.
If you cast Magic Missile with at least a 3rd level spell slot you can activate this launcher. You must concentrate on the spell as long as this launcher has missiles left. Should your concentration be broken, then all remaining shots are lost.
The spell loads the launcher and it can hold a maximum of 9 shots. It can be shot as an action that fires two missiles at one or two targets or one shot as a bonus action. Each missile does 1d4 + Intelligence modifier force damage.
Spiritual Sheath
Wondrous Item, Uncommon (Requires attunement by a spellcaster that knows Spiritual Weapon)
While it is labeled a "sheath", this item resembles a small jewelry box that has loops to be attached to a belt.
If you cast Spiritual Weapon at at least a 3rd level you may activate this sheath. The spell now lasts for 1 hour and can be housed in this item. Withdrawing or sheathing the weapon is a bonus action.
Note to Sender
Wondrous Item, Rare (Requires attunement by a spellcaster that knows Sending)
Upon closer inspection, this quill's entire surface is covered in arcane carvings. A popular item for those who'd rather text than talk...
Once per day, when you cast Sending while attuned to this quill, you can designate a sheet of paper and notify your target to do the same. You may continuously communicate using the designated sheet until both parties have written a total of 25 words. It can be done in multiple messages both ways.
Once a party has written 25 words, they may no longer write, but can still read messages until the other party has reached 25 words.
Beast Charm Bracelet
Wondrous Item, Very Rare (Requires attunement by a spellcaster that knows Summon Beast)
Often made of wood, these bracelets are popular gifts for more naturally inclined individuals. This item is geared towards allowing its owner to carry spiritual companions in portable forms.
Artist Credit: Viktor Solovyov via Artstation
When you would cast Summon Beast at 3rd level or higher while attuned to this bracelet, you may instead create a single charm attached to it. As a bonus action, you may pull off a charm from this bracelet to summon the beast you chose when creating the charm and begin concentrating on the spell.
This bracelet can hold up to two charms. Any charms remaining disappear at the end of a long rest.
Lightning Rod
Wondrous Item, Very Rare (Requires attunement by a spellcaster that knows Witch Bolt)
This is actually a silvered tree branch hewn from a tree struck by lightning. Its composition allows it to be a powerful material when used to cast certain spells.
When you would cast Witch Bolt at 2nd level using this as a focus, you may also throw this rod at a square within 30 feet and target it with the spell. Any creatures within 5 feet of the Lightning Rod take 1d12 lightning damage plus another 1d12 for each spell level above 2nd level initially. You can use your action to deal 1d12 lightning damage to the rod automatically and all creatures within 5 feet of it. Concentration ends only if you take another action. A move action, or moving the rod does not end the spell.