Tower Shield of the Rein (5e Equipment)
From D&D Wiki
Long ago a group of heroes known as, "The Crusaders". Their leader, who is known as The Rein, wielded a powerful shield which could withstand the might of a dragon's fury. But one day The Crusaders fell and this once mighty shield was lost to the decays of time.
Heavy : If a character does not meet the prerequisite of Strength, they can still attune to it but they suffer disadvantage to all Dexterity checks and saving throws and lose 10 feet of movement speed. Anyone who attunes to it who has an 17 Strength does not suffer the disadvantages in Dexterity but they still lose the 10 feet of movement speed. Anyone who attunes to this shield with 21 or higher Strength does not suffer the speed reduction.
Shield Properties: The shield is 7 feet tall and weighs 60 pounds. This shield provides you with a +3 bonus to AC. When you take the Dodge action with this shield out, you gain 3/4 cover.
Rememberence: When the shield is hit by a breath attack of the dragon of the same color as the shield, the voice of Rein will be heard by the current wielder of the shield of him saying, "The Shield has accepted you". The shield will break into quarters exposing a larger version with the eagle being a part of the center and the black lines becoming a cross with the shield becoming up to 10 feet tall and 15 feet wide, covering the square to the wielder's right and left by one square from all effects of that dragon attack. The shield can then compact back to the regular "unremembered" form and can be switched through forms via an action. The wielder cannot make attacks or use spells that have a somatic component when the shield is in its large form, which provides full cover to you and the creature's to the left and right of you.