This feature gives the players the option to select synergy bonuses from 10 heroes at any one time. They will be rewarded for having heroes at level 25 and level 50.
Press V to see open the achievements pane, which includes Hero Synergies. A full achievement system is coming this Fall.
Adjust and “Apply Changes” in hub or training room. No cooldown or cost to change. (Take notes from my forum post to make this awesome)
As mentioned by the devs:
The Marvel universe is filled with stories about heroes supporting each other, swooping in to save the day or just providing logistical support to their teammates behind the scenes. The Hero Synergy System captures some of that feeling and provides an in-game reward for players who've established a solid bench of heroes.
This is how it works:
(1) A new interface screen allows you to control which synergies you have selected for which hero. Press V to go to this screen. The screen is called Achievements and will also house the achievement system that is planned for later this fall.
(2) Each of your heroes can select completely customized synergies from the ones you have available. A hero is welcome to use their own synergy if they wish.
For example: You could focus on melee and survivability synergies for 
Hulk and ranged and crit chance synergies for 
Cable.
(3) Whenever you level up a hero to 25, it unlocks a synergy that becomes available to slot into your list of 10. If you level the hero to 50, it can make that synergy stronger or offer a different additional synergy.
For example: 
Black Panther unlocks a movement speed buff for your heroes at level 25 and a melee damage buff for your heroes at level 50. If you pick Black Panther as one of your 10 “slots” for a hero, they will get both bonuses.
(4) All of the hero synergies are flavored for the heroes. Cable synergies buff crit chance, 
Wolverine synergies buff brutal strikes, 
Rocket Raccoon synergies buff pets, 
Scarlet Witch buffs damage with DOTs, etc.
(5) There is no cooldown or limit to the number of times you can adjust synergies for each of your heroes. As long as you are in a hub or training room.
(6) Every time a new hero is added to the game, they will bring new synergy options with them.
Example: Luke Cage brings an option to select Defense and Melee Damage buffs for your heroes. Squirrel Girl is the ultimate Doctor Doom slayer and bring buffs to damage against supervillian bosses.
(7) Activate synergies by toggling the corresponding buttons on the Synergy System panel. Once you toggle on the synergy and click "Apply", you will activate those buffs for your current hero. You can adjust and save these for each of your heroes.
The final bonuses are still in heavy testing and iteration, but here is a preview:
Black Panther has the only move speed buff (earned when you level Black Panther to 25) and provides a melee damage buff at 50. The level 25 synergy is very useful for leveling new heroes and the level 50 synergy is very useful for end-game.
Black Widow provides stealthy covert buffs – bonus damage against targets not attacking you. This is nice for ranged heroes, pet classes and stealth classes.
Cable has simple buffs – bonus to critical hit chance.
Captain America gives your heroes a chance to deflect projectiles – extremely powerful for melee and ranged heroes survivability.
Colossus provides a sturdy health bonus when leveled to 25 and a solid tenacity bonus at level 50. Good for almost all heroes, but particularly melee heroes.
Cyclops gives the obvious bonus to energy damage at level 25 and is the one hero who provides an experience bonus buff when he reaches level 50 and has established himself as a team leader.
Daredevil is the ultimate henchman hunter. He offers a damage bonus against all normal and elite enemies.
Deadpool has a special role in the Marvel universe as the hero who breaks the 4th wall. He offers an item rarity and special item find boost at level 25 and 50, respectively.
Emma Frost provides a bonus to AOE damage at level 25 and provides a chance to deal mental damage on hit at level 50.
Hawkeye’s deadly precision allows him to provide a bonus to critical damage at level 25 and 50.
Hulk offers bonus health at 25 and 50. He is the only hero that offers both levels of health buff.
Human Torch is the ultimate AOE machine and provides a damage boost to AOE and both level 25 and 50.
Iron Man is useful to ranged heroes and energy damage heroes, providing a damage bonus to both.
Jean Grey offers a strong bonus to both mental damage and energy damage.
Luke Cage offers bonus damage to defense (his trademark unbreakable skin) and melee damage – he’s the ultimate street fighter.
Ms. Marvel is pure damage – A bonus to energy damage at both level 25 and 50.
Punisher bonuses directly reward killing, granting a health and spirit bonus on kill.
Rocket Raccoon offers strong bonuses to health and damage of summoned pets and minions. Useful for many builds of various heroes.
Scarlet Witch buffs damage with DOTs, very solid for certain builds on many heroes.
Spider-Man has the best dodge in the Marvel Universe and offers bonus dodge to your heroes, currently the most efficient survivability stat, at level 25 and 50.
Squirrel Girl has defeated Wolverine, Doctor Doom and even Thanos. Her buff is bonus damage to bosses for all types of attacks.
Storm offers a bonus to Spirit, a stat important to all heroes and regarded highly by advanced players of many heroes.
Thing really wants to tank. He gets a damage bonus to foes attacking him.
Thor brings melee and lightning damage to the mix with a melee damage bonus at 25 and a lightning bolt proc at level 50.
Wolverine is the most brutal of the group, with brutal strike chance at 25 and brutal damage at 50.
List of Synergy[]
| Hero | Lvl 25 | lvl 50 |
|---|---|---|
 Black Panther
|
+3% Move Speed | +2% Melee Power Damage |
 Black Widow
|
+2% Unaware Target Damage | +2% Unaware Target Damage |
 Cable
|
+1% Critical Chance | +1% Critical Chance |
 Captain America
|
+2% Deflect Projectile Chance | +2% Deflect Projectile Chance |
 Colossus
|
+3% Health | +2% Physical Damage |
 Cyclops
|
+2% Energy Damage | +10% Bonus XP |
 Daredevil
|
+3% Damage vs. Normals/Elites | +2% Melee Power Damage |
 Deadpool
|
+10% Rare Item Find | +10% Special Item Find |
 Dr. Strange
|
+2% Mental Damage | +2% Mental Damage |
 Emma Frost
|
+2% Area Power Damage | 2% Psi Blast on any hit |
 Gambit
|
+5 Credits per Drop | +10% Rare Item Find |
 Ghostrider
|
+2% Mental Power Crit Chance | +2% Mental Power Crit Chance |
 Hawkeye
|
+2% Critical Damage | +2% Critical Damage |
 Hulk
|
+3% Health | +3% Health |
 Human Torch
|
+2.5% Area Power Damage | +2.5% Area Power Damage |
 Invisible Woman
|
+2% Energy Damage | +2% Deflect Projectile Chance |
 Iron Man
|
+2% Ranged Power Damage | +2% Energy Damage |
 Jean Grey
|
+3% Mental Damage | +3% Energy Damage |
 Juggernaut
|
+3% Movement Power Damage | +3% Movement Power Damage |
 Loki
|
+5% Damage to Slowed Targets | -5% Spirit Cost for Powers |
 Luke Cage
|
+2% Defense | +2% Physical Damage |
 Magneto
|
+4% Area Power Damage | +10% Orb Pickup Radius |
 Moon Knight
|
+2% Physical Power Crit Chance | +2% Physical Power Crit Chance |
 Mr. Fantastic
|
5% Crafting Discount | +4% Critical Damage |
 Ms. Marvel
|
+2% Energy Damage | +2% Energy Damage |
 Nightcrawler
|
+2% Melee Power Damage | +2% Melee Power Damage |
 Nova
|
+3% Move Speed | +2% Dodge Chance |
 Psylocke
|
+3% Mental Damage | +3% Physical Damage |
 Punisher
|
Health on enemy defeat | Spirit on enemy defeat |
 Rogue
|
Health on any hit | 1 Spirit on any hit |
 Rocket Raccoon
|
+5% Pet and Minion Damage | +5% Pet and Miniom Health |
 Scarlet Witch
|
+2% DoT Power Damage | +2% DoT Power Damage |
 Silver Surfer
|
+3% Move Speed | +2% Energy Damage |
 Spider-Man
|
+1% Dodge Chance | +1% Dodge Chance |
 Squirrel Girl
|
+2% Damage vs. Bosses | +2% Damage vs. Bosses |
 Star-lord
|
+2% Energy Power Crit Chance | +2% Energy Power Crit Chance |
 Storm
|
+10 Spirit | +10 Spirit |
 Taskmaster
|
+1% Projectile Deflect Chance, 1% Dodge Chance | +1% Critical Damage, +1% Melee Power Damage |
 Thing
|
+2% Attacking Target Damage | +2% Attacking Target Damage |
 Thor
|
+3% Physical Damage | 3% Energy Damage |
 Venom
|
+3% Health | +5% Damage If Below 50% HP |
 Wolverine
|
+2% Brutal Strike Chance | +5% Brutal Damage |
 X-23
|
+2% Damage vs Bleeding | +2% Damage vs Bleeding |
