Permanent Potion of Growth (5e Equipment)
From D&D Wiki
Potion, Very Rare
When you drink this potion, your size doubles in all dimensions and your weight is multiplied by eight. This growth increases your size by one category, Medium to Large, for example. If there isn't enough room for you to double your size, you obtain the maximum possible size in the space available, but the potion's effect becomes temporary if this occurs, lasting just as long as a normal variation of the potion. Additionally, your Strength score is raised by 1 point if the increase is from Tiny size to Small size, 3 points if the increase is from Small to Medium size, 6 points if the increase is from Medium to Large size, 9 points if the increase is from Large to Huge size, and 12 points if the increase is from Huge to Gargantuan size (You absolute monster, you). In ANY case, this change cannot raise your Strength score above 30, though the change in size still raises things like how that score works mechanically (For things like carry capacity, for example). This effect cannot be ended by effects that end spells or prevent spells from being cast, and is effectively the new natural size of you. Weapons, clothing, and items will change size under this effect, with weapons dealing an additional die of damage of the weapon's damage dice types (This change is cumulative, with weapons gaining an additional damage die each time their size is increased this way). Any such items also do not revert their form when they leave your hand, nor do items you acquire afterwards alter their size to be larger (Unless the item explicitly is meant to do this).
If by some insane nature of the DM you can drink more than one of these, the increase to your Strength score is raised by 1 cumulatively each time (Maximum 3 additional points to the score). This means that the 2nd potion raises your Strength by 7 points instead of 6 if the increase is from Medium to Large, and a 3rd potion raises this increase to 8 (From Medium to Large), affecting every size category shift and accompanied score increase the same way.