This is one of the first colorless ways we've seen to rock indestructible for your team and keep them alive against a Nevinyrral's Disk
Unlike Cavern of Souls, Delighted Halfling can be tapped for any mana to cast any legendary artifact, legendary enchantment, and even legendary sorcery spell like Karn's Temporal Sundering
Some cards return a card to the battlefield, usually a creature card, for one last chance at life
They don't copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on
Whenever you sacrifice another permanent, you gain 2 life if this is the first time this ability has resolved this turn
If you want a more traditional avenue through combat damage, Patron of the Vein in a Vilis Vampire tribal deck, or just huge Yahenni, Undying Partisan would be the way to go