Hellish vigour warhammer fantasy battle 8th edition lore of the vampires spell overview
Hellish vigour is a new spell for vampire counts in warhammer 8th edition fantasy battle (though I suspect it did exist in a previous incarnation possibly under a different name) nor was there a spell with a similar effect.
Hellish vigour is an augment type spell that gives the target friendly undead unit it is cast on the ability to re roll to wound in close combat. It has an even more powerful area effect version which grants this augment effect to all friendly undead units within 12" of the caster. Of course this area effect version of the spell has a much higher (double) casting level. It last through the rest of your turn until the beginning of your next magic phase so lasting through your opponents turn. this gives you the benefits of hellish vigour for two rounds of close combat.
Like all the lore of the vampire spells it benefits from the curse of undeath lore attribute allowing you to heal a wound to the caster or another nearby friendly model. Both the spell and the lore attribute have a maximum range of 12" making both quite short ranged and meaning your wizard will need to be near the action.
Hellish vigour is only useful in melee combat though alternatively you could use it to augment a unit to dissuade your opponent from charging it. It is also short ranged so the wizard with it needs to be near (necromancer) or in the middle of the fight (vampire). It is best combined with a charge where maximum damage will be done to the enemy, it can also bolster a unit fighting a particularly tough opponent.
Re roll to wound synergises particularly well with unit and characters with killing blow namely grave guard, black knights, wight kings and Krell (and occasionally black coaches). This is because beside giving them a second chance to wound it gives them a second chance to get that killing blow.
Hellish vigour also synergises well with the vanhel's danse macabre spell and/or the vigour mortis special ability from the corpse cart. The combination of always strikes first, re rolls to hit and re rolls to wound can turn even zombies into a force to be feared and augments more powerful units much more. Also worthy of a mention is the extra attack granted by the staff of damnation. A unit of blood knights, black knights or grave guard under these effects will slaughter just about anything before them.
Taking numerous wizards with the lore of the vampire and either Heinrich Kemmler or Mannfred von Carstein will ensure that you get this spell. Heinrich and Mannfred ensure that you can make sure you have a wizard who can cast it where you want it.