mtg sacrifice draw a card MTG-4x-Near Mint, English-Sanguine Statuette - Foil-Innistrad: Crimson Vow then you gain life equal to its toughness. MtG Rise of the Eldrazi

however, the payoff is too big to ignore

It answers a weakness many tribal strategies have, which is being vulnerable to spot removal

P/T Number 35 Language English Legal Formats Commander, Legacy, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Historic, Modern, Pauper, Pioneer, Standard, Timeless Rulings (12/7/2018) Iridescent Drake's triggered ability can target any Aura card in a graveyard

Six mana makes this very difficult to justify

The delve isnt just for making it cheaper either though, as itll enter with a +1/+1 counter on it for every instant and sorcery you exile to pay for the delve part of the cost

At eight mana, it destroys three, but eight mana is a massive amount to spend on any one spell