Firebreathing

Firebreathing is any mechanic that pays homage to the original Firebreathing card; that is, ": This creature gets +1/+0 until end of turn". This mechanic was featured on the card Shivan Dragon in Alpha and, in general, is a trademark of most dragons. It's most often seen on red creatures. White tends to get one-time upgrades of usually +1/+0. Green gets +N/+0 when it's not intended for it to survive the fight.

Color cost variations

 * Moltensteel Dragon and Immolating Souleater have a phyrexian version of it ": This creature gets +1/+0 until end of turn"
 * Soldevi Simulacrum and Snow Fortress have generic costed firebreathing.  Lavaclaw Reaches has an  cost variant (relevant for cost reducers), though it requires  to animate initially. Steel Hellkite, Narstad Scrapper</c> and Dragon Engine</c> have a generic version of it ": This creature gets +1/+0 until end of turn". Incited Rabble</c> has  also, and starts as a white creature.
 * Moonveil Dragon</c> does have a similar ability ": Each creature you control gets +1/+0 until end of turn."
 * Blistering Dieflyn</c>, Henchfiend of Ukor</c>, and Duergar Cave-Guard</c> can activate firebreathing with half-red hybrid mana in the cost; ": This creature gets +1/+0 until end of turn" for the former pair and ": This creature gets +1/+0 until end of turn" for the latter. All three creatures are monocolored red.
 * Scourge of the Nobilis</c> grants firebreathing to its target, if it is red; this is the only one of the four which can be used to grant 1-to-1 firebreathing with entirely nonred mana.
 * Vaevictis Asmadi</c> has the unique cost of triple-hybrid firebreathing, for, , or.
 * Sea Spirit</c>, Viscerid Deepwalker</c> and Wall of Water</c> hold "waterbreathing", functionally identical to firebreathing in Blue. With a party, Seafloor Stalker</c> can reduce its ability to a single . Dirtwater Wraith</c> has another version in Black.
 * Kozilek's Shrieker</c> has colorless-based firebreathing, in addition with menace. Icehide Troll</c> and <c>Grim Draugr</c> have snow-breathing.

Creature colors

 * <c>Stone Kavu</c> and <c>Steam Spitter</c> are the only mono-green creatures with firebreathing. <c>Cavern Thoctar</c> has a weaker variant.
 * <c>Firescreamer</c> is the only mono-black creature with firebreathing.
 * <c>Angelfire Crusader</c> is the only mono-white creature with firebreathing.

Granting

 * <c>Dragonrage</c> is the only instant that can grant firebreathing.
 * <c>Brood Keeper</c> and <c>Dragon Egg</c> both make Dragon creature tokens with firebreathing.
 * <c>Ghitu War Cry</c>, <c>Captive Flame</c>, and the flip card <c>Homura's Essence</c> are the only non-Aura Enchantments that grant firebreathing.
 * A number of Auras grant the enchanted creature firebreathing, including <c>Dragon Mantle</c>, <c>Crown of Flames</c>, and <c>Ghitu Firebreathing</c>.

Other

 * Modern design has moved away from the literal : +1/+0 ability due to its monocolor restriction; <c>Hellkite Punisher</c> was the first in four years since <c>Skyship Stalker</c>. Most designs now use as a basis, using worse ratios on better bodies (<c>Incendiary Oracle</c>, <c>Rakdos Trumpeter</c>), or one-to-one on worse bodies (<c>Igneous Cur</c>, <c>Weaselback Redcap</c>). This is to support decks being two-colored, as expected for decks of newer players and drafters.