Vampirism is a powerskill which that consumes a portion of player's health in exchange for a leech effect of player's melee attacks and a speed boost for 10 seconds.
Upon usage, player loses an amount of health equals [40% base, 20% max] max health. For 10 seconds, the player's movement speed is increased by 20%, and all of their melee hits heal 2% max health.
Heavy melee weapons (which have the "Cannot be interrupted by an enemy's attack" affix) heal 4% max health instead.
The healing effect has a cooldown of 0.25 seconds.
"Extends the effect by 2 seconds upon killing an enemy."
Synergies
Vampirism provides a speed buff, allowing the Swift Sword to deal critical damage.
Vampirism provides a speed buff, allowing for healing from the Frenzy mutation, which stacks with the healing provided by vampirism itself.
Notes
The skill cannot be activated if the player is at 0% max health.
Due to not actually having the "Has Duration" tag, this skill cannot receive the extended duration affix.
Melee attacks that aren't dealt by weapons, such as the dive attack or the Phaser skill will heal the player for 2% of their maximum health while this skill is active.
Projectiles fired by items classified as melee weapons will not provide healing from vampirism, such as Rhythm n' BouzoukiTBS,s third repeated attack, Wrecking BallTQatS's third (The throw) and fourth (The recall) attacks, the Maw of the DeepTQatS's third attack, and the falling stars summoned by Starfury.
Strategies
Since vampirism heals the player per successful melee attack and is independent of damage, it is worth choosing faster, less burst oriented melee weapons such as Panchaku, Abyssal TridentTQatS, and Balanced Blade.
The power Pollo Power does rapid melee attacks, allowing for great healing with vampirism.
Note that vampirism must be activated before pollo power, as activating pollo power will prohibit the player from using vampirism.
Despite not being mentioned in the item's description, heavy weapons (Weapons tagged "HeavyWeapon" in the source files) heal 4% of the player's max HP instead of 2%. This is to mitigate the HP loss that would otherwise be caused by the lesser speed of these weapons. The fastest, and therefore the best heavy weapons to heal with vampirism are Death's ScytheRtCIron StaffFF, Ferryman's LanternFF, Shovel, and Nutcracker.
In biomes, much of the player's time may be spent seeking after enemies, this will waste vampirism's active period. And so without further planning, vampirism is generally only effective when fighting bosses.
Bosses that have periods of invincibility, such as The Hand of the King and Mama TickTBS can waste vampirism's active period.
Using off color weapons (Using Panchaku when survival is the highest stat, or using Death's ScytheRtC when brutality is the highest stat.) makes it possible to land the most strikes without dealing lethal damage, removing the need to seek out multiple enemies.
Striking multiple enemies with the same attack counts as landing multiple melee attacks, so bringing multiple enemies close to each other by getting them to chase you (Most easily done on four Boss Stem Cell+, when most enemies can teleport) will allow for great healing.
This is most easily done when playing survival, as Tonic can be used to more safely deal with mobs of enemies.
Because the damage output and status effects caused by Ice Grenade, Frost Blast, and Ice ArmorRotG only scale with survival, they are more efficient for this task when playing brutality.
Because the damage increase and status effects caused by the power Smoke BombTBS do not scale with survival, it is more efficient for this task when playing survival.
Possible Affixes
Minor Affixes:
Colorless (on legendary, on first time completing the blueprint, or through custom mode)
No longer transforms health into recovery. Instead, sacrifices a portion of max health to give a leech buff on melee attacks and a speed boost for 10 seconds.