Shadow of the Second Sun is a mythic Enchantment — Aura card from Modern Horizons 3 (MH3), collector number 402. Current market price: $1.15 (foil $5.03), TCGplayer market prices via Scryfall.
Enchant player At the beginning of each of enchanted player's postcombat main phases, there is an additional beginning phase after this phase. (The end step happens after the added untap, upkeep, and draw steps.)