Manifesting a card puts it onto the battlefield as a 2/2 creature, and you can turn it face-up by paying its mana cost
Legendary Creature Enchantment - God Color tag templates(None) Horizon Chimera Flash Flying, trample Whenever you draw a card, you gain 1 life
Sorcery Color tag templates(None) Green Sun's Zenith Search your library for a green creature card with mana value X or less, put it onto the battlefield, then shuffle
~ Mythic Rare Allied Color Creatures: Four mythic rare creatures that are of an allied pair associated with one of four monster tribes associated with Innistrad Drogskol Reaver, Falkenrath Aristocrat, Havengul Lich, and Huntmaster of the Fells
You just need to test and test and test some more to feel out what works and what doesnt
Playing sideboard cards that are only good against Burn is likely a losing battle, no matter how good Kor Firewalker or Dragon's Claw might be in the Burn matchup