Heroic

"Your enemies are as numerous as they are ferocious; their attacks are devastating. Survival is not guaranteed."

- Description from Halo: Combat Evolved, Halo 2, Halo: Combat Evolved Anniversary, and Halo: The Master Chief Collection.

"Fight against formidable foes that will truly test your skill and wits; this is the way Halo is meant to be played."

- Description from Halo 3, Halo 3: ODST and Halo: Reach.

"Fight against foes that will truly test your skill - this is the way Halo is meant to be played!"

- Description from Halo 4.

"Formidable opposition will test your resolve. Skilled, tactical play required. Recommended for veteran Halo players."

- Description from Halo 5: Guardians

Heroic is the second hardest difficulty in the Halo series campaign mode.

Summary
The symbol for the Heroic difficulty setting in the trilogy is represented with a shield that has the Marathon logo encrusted into the center; over the shield are two UNSC machetes crossed over each other. In Halo 3: ODST, it is represented by two silenced SMGs crossed over a shield with the Marathon symbol encrusted into the center.

Heroic pits you against the Covenant, who are now slightly smarter, and their weapons inflict more damage per hit than their Normal-level counterparts. Even the weakest of infantry, the Grunts, can withstand quite a few bullets before they go down. It is otherwise considered "Hard", in other games. Although in Normal Master Chief, The Covenant and the Marines have a more reasonable strenght and health, Bungie has stated that Heroic difficulty is the "true Halo universe", due to the fact that in Heroic enemy numbers and accuracy are more realistic.

The following are a list of changes in the Heroic difficulty:
 * Health meter is smaller. Hits do more damage.
 * Shields are only 75% their "Normal" capacity.
 * Increased Shields and/or armor for enemies.
 * Many Minor Elites are replaced by Major Elites. Major Grunts are more frequent as well, along with other opponents.
 * Enemies are smarter regarding tactical actions, and are thus harder to kill (ex. starting to hide behind barriers when their shields are down).
 * Marines have reduced effectiveness and are weaker; their tactical intelligence has also been reduced.
 * Ultra Elites and Ultra Grunts appear ever so often and for the Elites, they normally dual wield.
 * Many more Jackal snipers are placed throughout levels, and in Halo 3 and Halo 3: ODST, some of them have Beam Rifles instead of Carbines.
 * The numbers of enemy forces will be increased.

All of these wrap up into a nice gameplay option for more experienced players, who find Normal less exciting, and Legendary too hard. This difficulty may be deemed the most realistic by some players; however, this is not to be stated as a fact, as each player has his/her own comfort zone, regarding difficulty.

In Halo 3, Heroic was intended for those who have played the prior games and multiplayer, resulting in increased skill. This increase means that those who found Normal comfortable in Halo 2, will find Heroic just right for Halo 3, according to Frankie. Martin O'Donnell stated that, 'Normal is for beginners who are embarrassed to pick Easy. Heroic is what we intended.'

Trivia

 * Every difficulty shield icon has the Marathon symbol on it except in Halo: Reach.
 * Halo 3 , Halo 3 ODST , and Halo: Reach keep track of whether you finished Heroic Campaign on Solo or Co-op.
 * In Halo 3, you unlock Elite Flight armor for beating Campaign on Heroic difficulty.

Related links

 * Campaign Complete: Heroic