Vampire Warlord

• WWizards of the Coast2013-07-01
  Official Ruling
  If Vampire Warlord is dealt lethal damage and is dealt damage by a source with deathtouch during the same combat damage step, a single regeneration shield will save it.
• WWizards of the Coast2013-07-01
  Official Ruling
  To work, the regeneration shield must be created before Vampire Warlord is destroyed. This usually means activating its ability during the declare blockers step, or in response to a spell or ability that would destroy it.
• WWizards of the Coast2013-07-01
  Official Ruling
  Activating Vampire Warlord’s ability causes a “regeneration shield” to be created for it. The next time that creature would be destroyed that turn, the regeneration shield is used up instead. This works only if the creature is dealt lethal damage, dealt damage from a source with deathtouch, or affected by a spell or ability that says to “destroy” it. Other effects that cause the creature to be put into the graveyard (such as reducing its toughness to 0 or sacrificing it) don’t destroy it, so regeneration won’t save it. If the regeneration shield isn’t used, it goes away as the turn ends.

Rulings via Scryfall