Vampires can copy Strength Combat Strength values of all land and naval units except Giant Death Robots and Heroes introduced in the Heroes & Legends game mode. Note that they can copy the Strength Combat Strength of Corps/Armies and Fleets/Armadas, but not aircraft, and only if you trained/upgraded them. (For example, if you form a Corps from two existing Swordsmen, your Vampires won't copy the Corps' strength. However, if you train a new Swordsman Corps from the Encampment or upgraded an existing Warrior Corps into a Swordsman Corps, your Vampires will be updated to use the Corps' strength.)