Regen

If this card is killed in combat, return it to a battlefield you control your next turn.

Rulings
If a card kills it with Poison X rather than with combat, even though it was because of combat, it was not killed in combat, and thus will not return to the battlefield.

While uncommon, a card may have both regen and undead, most likely through the effect of another card. If this is the case, the player may choose which effect activates at the time to card returns to the field. If a card is Undead, and it dies, the player may use regen to return it to the field, but it becomes the type it was before it became Undead, and must die again before it can become Undead.