The Bhaalspawn are entities from the Forgotten Realms setting of Dungeons & Dragons, whose brief but dramatic influence on the realms occurred during a short period towards the end of 2nd edition.

As their name suggests, the Bhaalspawn are the semi-divine offspring of Bhaal, Faerun's God of Murder. Apparently warned by prophecy of his death during the Time of Troubles, Bhaal enacted a plan to resurrect himself; impregnating myriad women of myriad races, from the core PHB races to giants and dragons, Bhaal created an army of sons & daughters carrying slivers of his essence. In the event of his death, these Bhaalspawn would be compelled to fight and slay, both the mortals around them and each other, until the influx of murdered souls and slain Bhaalspawn would rejuvenate the slain Bhaal and restore him to life.

Amongst fans of Baldur's Gate, the /v/ trilogy that covers this plot, Bhaalspawn is generally used as the term for the protagonist.

Whilst there were never any official tie-in novels, and anyone who tells you otherwise is a damn liar, Dragon Magazine #288 included a Bhaalspawn racial template, allowing DMs to include Bhaalspawn villains or even feature Bhaalspawn PCs in their own games. Luckily for you, /tg/ gets shit done, so here's the crunchy stuff:

Bhaalspawn Template:

Level Adjustment: +2
Can be applied to: Dragon, Fey, Giant, Humanoid, Monstrous Humanoid, Outsider, or Shapechanger. The creature gains the Outsider type and retains all base qualities except where indicated otherwise.
Natural Armor Bonus +1
Favored Class changes to Sorcerer
Special Qualities: A bhaalspawn gains a number of Bhaalspawn Advantages, and an equal number of Bhaalspawn Penalties, determined by its Hit Dice, at the following rate: 1-3 HD gives 2 Bhaalspawn Special Qualities, 4-5 HD gives you 3 abilities, 6-7 HD gives you 4 abilities, 8-9 HD gives you 5 abilities, 10-11 HD gives you 6 abilities, 12-13 HD gives you 7 abilities, 14-15 HD gives you 8 abilities, 16-17 HD gives you 9 abilities, 18-19 HD gives you 10 abilities, and 20+ HD gives you 11 abilities, at which point you can't get any higher.
You cannot take an Advantage or a Penalty more thn once, although one would argue that some traits, such as Cold Resistance, Fast Healing, and Charisma or Wisdom Loss ought to be exceptions to the rule.
Spell-like abilities granted as Bhaalspawn Advantages all cast with a caster level equal to the Bhaalspawn's character level.

Bhaalspawn Advantages:

  • Bull's Strength (Sp): 3/day
  • Cold Resistance (Ex): 5
  • Cure Moderate Wounds (Sp): 3/day
  • Damage Reduction (Su): 5/Silver
  • Darkness (Sp): 3/day
  • Death Knell (Sp): 3/day
  • Endurance (Sp): 3/day
  • Fast Healing (Ex): Regains 3 hit points per hour so long as it has at least 1 hit point.
  • Fire Resistance (Ex): 5
  • Immortal Soul (Su): This bhaalspawn no longer accrues aging penalties and gains a +10 bonus to saving throws against death effects.
  • Poison Blood (Su): 1/day, a bhaalspawn with this trait who has taken at least one point of damage can smear its blood on a weapon, effectively applying a dose of deathblade poison.
  • Poison Immunity (Ex): This bhaalspawn is immune to poison.
  • The Slayer (Ex): As a standard action, this bhaalspawn can assume the form of the Slayer, which grants it claws that allow it to do 1d10 damage with its unarmed attacks (unless it would normally do more), +6 Natural Armor, and +8 strength. Slayer Form inflicts 1 point of temporary Constitution damage on the bhaalspawn per round they remain in it.
  • Scare (Sp): 3/day
  • Unholy Blight/Holy Smite (Sp): 1/day, a neutral Bhaalspawn must choose which spell they get when this trait is developed.

Bhaalspawn Penalties:

  • Battle Recklessness (Ex): Whenever a bhaalspawn with this trait is below half its maximum hit point total, it suffers a -1 morale penalty to Armor Class and to all attack rolls.
  • Blood Thirsty (Ex): A bhaalspawn with this trait must succeed on a DC 20 Will save to be allowed to inflict subdual damage with its attacks. Additionally, if it has multiple attacks, it must succeed on a DC 20 Will save when facing multipe foes or split its attacks amongst as many foes as possible.
  • Called To Hell: A bhaalspawn with this trait that is reduced to 0 or negative hit points enters a deep coma and cannot regain consciousness until healed to at least half its total hit points.
  • Charisma Loss: -2 Charisma
  • Demon's Blood (Ex): When a bhaalspawn with this trait is bleeding, evil outsiders can detect and track it as if they had the Scent quality.
  • Haunted (Ex): Undead within 60 feet are always aware of the presence of a bhaalspawn with this trait; even when under Invisibility To Undead, they remain aware that something is occupying the space that the bhaalspawn is in.
  • Infernal Temper (Ex): If a bhaalspawn with this trait fails any skill check by more than 5, or is taunted, goaded or humiliated in some manner, then it must take a Will saving throw (DC 10 + amount the check was failed by). A failure causes them to suffer a -1 morale penalty to all skill checks until they succeed at a skill check by more than 5.
  • Murderer (Ex): Once every 13 days, a bhaalspawn with this trait must kill an NPC with an Int of 3+ that would not normally have a Hostile attitude towards them. If they refuse to kill on the deadline, then they suffer 1 point of Wisdom damage each day until they submit, which can drop them to a minimum of Wisdom 3. No magical or normal means can heal this Wisdom damage, but it is instantly healed once the bhaalspawn murders a victim.
  • Nightmares (Su): Each time this bhaalspawn rests, it must succeed on a Will saving throw (DC 10 + 1 per day the nightmares were resisted), or throw a 1d4 to see what effect it suffers:
    • 1: -2 morale penalty to attack rolls.
    • 2: -1 morale penalty to all saving throws.
    • 3: No damage is healed for resting.
    • 4: The bhaalspawn faces their demons and triumphs, suffering no penalty.
  • Supernatural Infamy (Ex): On a first meeting with a bhaalspawn with this trait, no NPC can have an initial attitude better than Unfriendly.
  • Tainted With Evil (Su): This bhaalspawn is always treated as an evil creature for spells, spell-like effects, and supernatural abilities, regardless of actual alignment. If their alignment is Evil, they now take damage from holy water.
  • Wisdom Loss: -2 Wisdom

As pointed out in the Dragon Magazine article, for anyone wanting to use this template, it should be taken into consideration that all bhaalspawn hail from around the Times of Trouble, roughly 1358 DR. With the default starting year of 3.5 Forgotten Realms being 1372 DR, it'd make anyone sired by Bhaal shortly before his death a mere 14 years old. However, given that there is precious little child murder in the bhaalspawn saga, a game series that culminates in 1368 DR, and us knowing that Bhaal even fucked dragons, such issues can probably be dismissed.

Slayer can be maintained indefinitely if the character has some way to negate the con damage. This can be achieved with Strongheart Vest or a level in Binder to bind Naberius.