This list goes beyond the obvious
Rift Bolt
, which with suspend can fuel
Chandra's Incinerator
the following turn for no mana, with
Seal of Fire
for a similar effect. Played turn one, either can help get Incinerator into play as early as turn two. 

Vexing Devil
Vexing Devil
Magic: The Gathering
Rare

When Vexing Devil enters the battlefield, any opponent may have it deal 4 damage to them. If a player does, sacrifice Vexing Devil.
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A clever inclusion is
Vexing Devil
, which by dealing 4 damage to the opponent goes farther than the typical burn spell for enabling
Chandra's Incinerator
. The downside of
Vexing Devil
that keeps it from play in normal burn decks is that creatures are easier to interact with than burn spells, which get around both removal and blockers. Instead of avoiding creatures, this deck leans into them, hopefully exhausting removal and paving the way for
Chandra's Incinerator
to take over the game.