Whenever a land enters the battlefield under an opponent's control, if that player controls more lands than you, you may put a land card from your hand onto the battlefield
Lifegain effects fall into two categories: single-effect, big bursts of lifegain from cards like Feed the Clan, and incidental lifegain from cards like Soul Warden and Kambal, Consul of Allocation
Cards that passively scale with time and synergize well with support pieces are commonly valued by Commander players, which explains its listing between 13 and 17
Two mana to discard two cards is also just an incredible price, and is especially potent when Hymn to Tourach follows a turn-one discard spell like Thoughtseize or Inquisition of Kozilek
Then if there are seven or more time counters on it, remove those counters and it deals 20 damage to you
Add these two cards in a single one and we have edict/life drain in the same card slot