Absorption is a perk that is selectable from the beginning of the game. When using the perk, any time you use a basic ability, it will permanently add maximum energy and energy restoration to your hero. This effect will stack up to 100 times. This perk is great for those who constantly need energy for their abilities where their cooldowns are up long before the energy is available.
Absorption is a great pair with the perk Compartmentalization, as Compartmentalization uses max energy instead of minerals for each step. By using abilities, you are able to easily offset the cost of Compartmentalization and basically have the perk for free, with free (and quick) energy restore throughout the game.