<p>The answer is <strong>YES </strong>they stack. </p><p>When the charm is activated you inflict an elemental or physical damage equivalent to 5% of this creature's life, it means that you are dealing a damage to the creature, so if you have a prey of attack on the same creature it will be applied at the damaged dealed by the charm too. Take a look at the example</p><p><img src="https://vignette.wikia.nocookie.net/tibia/images/8/85/Skeleton_Elite_Warrior.gif/revision/latest?cb=20180607130119&path-prefix=en" alt="Skeleton Elite Warrior"> <em>Skeleton Warrior" src="https://vignette.wikia.nocookie.net/tibia/images/8/85/Skeleton_Elite_Warrior.gif/revision/latest?cb=20180607130119&path-prefix=en"> <em>Skeleton Elite Warrior</em> has <img src="https://vignette.wikia.nocookie.net/tibia/images/a/a2/Health_Icon.gif/revision/latest?cb=20171230131347&path-prefix=en" alt="Health Icon"> 7800 Icon" src="https://vignette.wikia.nocookie.net/tibia/images/a/a2/Health_Icon.gif/revision/latest?cb=20171230131347&path-prefix=en"> 7800 hit points. He is 0% weak against any kind of damage, except for Holy Damage damage that he is 25% and imune to death damage. and Death damage which he is imune. So if you apply the charm Wound <img src="https://vignette.wikia.nocookie.net/tibia/images/a/a4/Wound.png/revision/latest?cb=20171121005708&path-prefix=en" alt="Wound"> at alt="Wound" src="https://vignette.wikia.nocookie.net/tibia/images/a/a4/Wound.png/revision/latest?cb=20171121005708&path-prefix=en"> at this creature, when activated it will deal a physical damage of 5% of his total life life, it means a hit of "390", but if you have a prey of attack 10 start (25% stars (25% more damage) on the <em>Skeleton Elite Warrior </em>the damage dealed by the charm rise to "487".</p>