They let you look at the top card of your library at any time, play lands, and cast Bird spells from there , and, most importantly, they double-trigger abilities that fire when a land or Bird you control enters the battlefield
1 - Fiendsmith Engraver Fiendsmith Engraver is the most important card in the Fiendsmith engine, as, besides being a starter, it recycles Fiend Light monsters from your graveyard, so it makes this archetype's grind game quite interesting
I mean its a gamble card (which is bad) that draws some cards, but it also does have a downside of sending cards from your deck to the GY (bad for some decks!!) to off-set its somewhat positive effect.
Kindler Supporter Discard a Energy from your hand in order to use this card
But you still need the raw card to be worth enough to absorb the fee