Because cumulative upkeep now uses age counters, Chisei, Heart of the Oceans can eat an age counter from a cumulative upkeep card, thus keep the cumulative upkeep cost manageable while also keeping the 4/4 flying creature alive
Heliod, Sun-Crowned Even if youre not trying to go infinite with the Walking Ballista combo, if you care about lifegain, you want Heliod, Sun-Crowned in your deck, or in the command zone as one of the best mono-white commanders
Prior to the spike, copies of Quicksilver Elemental were valued at $0.40
Sure, Pia Nalaar, Consul of Revival likes this card, and it may be the best 5-drop for that deck, assuming you ever want a 5-drop in there
Doubling Season [Best Enchantment for Token and Counter Strategies] Doubling Season doubles all tokens and counters your effects create