“ This is an idea for a basic weapon which I have adapted partially into a fighter subclass. Let me know what you think, because if it's any good, I may post the subclass.
Double Bulwark Shield
Melee weapon (martial, shield)
Category: Items
Damage: 1d6 per hand, 1d4 together
Damage Type: Bludgeoning
Item Rarity: Standard
Weight: 6
When wielding the Double Bulwark Shield in two separate parts, you gain +2 to your AC, +1 per hand.
When wielding two separate parts of the Double Bulwark Shield, you can take an action to bring the two halves of your shield together. Your movement is halved as long as the shield is brought together. If you move or attack after bringing your shield together this turn, you receive a +3 bonus to your AC. If you don’t move or attack after switching this turn, you and an ally directly behind you receive a +5 bonus to your AC. This action is known as Steadfast.
Once the shield is brought together, you may take a bonus action to become Steadfast even if you attack this turn. However, you may not move or attack after becoming Steadfast.
Taking apart your shield is considered a free action.”
“ Dust Elemental
https://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=1594
At the corner of air and earth elemental planes resides the dust Elemental, a growing threat to Parisia. With it's powerful choking attack, this creature is a threat to the city. More and more of them are appearing in town, spawned from the many dust devils, a frequent foe of the party, they come in size from 3 HD to 20 HD. Why are there so many? Why in the city?”
“ A circus is in town and while parading down the main street the animals suddenly break free from the cages. After surviving and assisting during the breakout the PCs are hired to help with the investigation. Who did this and why?”