Battle for Zendikar was the first set to have an explicit lifegain mechanical theme without a keyword: Serene Steward and Cliffhaven Vampire formed the basis of the archetype, enabled by cards like Vampire Envoy and Stone Haven Medic
But perhaps BREAK Pokemon will become much more powerful in future sets
Enigma Ridges, Echoir Echoir is a plane originally visited by Dack Fayden in his pursuit of the Planeswalker Sifa Grent during The Spell Thief the second comic series of four in IDWs original Magic run
TYPE Legendary Creature Human Monk ABILITY Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.) Whenever one or more creatures you control with power 7 or greater deal combat damage to a player, untap all creatures you control
EDH has tens of thousands of cards at it's disposal, so feel free to recommend changes and things you'd do differently in the comments
Tiers Tier 1: Dragon Shield (original and matte), Player's Choice Japanese, Ultra Pro Pro Slayer, HCD Art Sleeves