Permanent Potion of Diminution (5e Equipment)
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When you drink this potion, your size is halved in all dimensions, and your weight is reduced to 1/8th of its normal. This reduction reduces your size by one category, Medium to Small, for example. Additionally, your Strength score is lowered by 1 point if the reduction is from Small to Tiny size, 3 points if the reduction is from Medium to Small size, 6 points if the reduction is from Large to Medium size, 9 points if the reduction is from Huge to Large size, and 12 points if the reduction is from Gargantuan to Huge size. In ANY case, this score cannot be reduced below 3 from this change. 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 1/2 damage as a result (This cannot reduce weapon damage below 1, but can be cumulative, reducing damage to 1/4th the roll if reduced again this way, or 1/8th damage from the roll if reduced again. Damage modifiers are unaffected by this reduction). 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 smaller (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 reduction to your Strength score is lowered by 1 cumulatively each time (Minimum 1 point of reduction). This means that the 2nd potion lowers your Strength by 2 points instead of 3 if the reduction is from Medium to Small, and a 3rd potion lowers this reduction to 1 (From Medium to Small), affecting every size category shift and accompanied score reduction the same way.