#1. Chanter - Crystal Maiden

Chanter

Gospel

Gives additional energy regeneration to all nearby friendly heroes.

Crystal Maiden

Arcane Aura

All allies' mana regeneration is increased.

They got nearly the same skill and position in the army, but their synergy is what make them different from each other. Crystal Maiden's ultimate fit perfectly for the 6 mages combo of the Auto Chess army which makes her one of the must-buy hero if you go mage, a very strong combo in the late game. Chanter synergy is good, but not that perfect as Crystal Maiden because energy regeneration is not a critical stat of Psyker/Supporter heroes. However Chanter cost only 1 gold, Crystal Maiden cost 2.

#2. Dreadpaw - Lycan

Dreadpaw

Call of Nature

Increase maximum Health and summons 2 wolves.

Lycan

Transform

Lycan assumes his lupine form, gaining more HP and summoning 2 wolves.

Lycan and Dreadpaw are just like twin brothers, from their appearance to skill and price cost (3 golds). Even their popularity is also the same. Both of them are excellent early and mid game hero with a powerful ultimate ability and easy synergies to assemble (Warrior/Beast with Lycan and Beast/Summoner with Dreadpaw). They scale well into the mid and late game as a level 2 unit, but isn’t a pure “tank” like other Warriors and is best played on the edges of a frontline instead of the middle.

#3. Blademaster - Juggernaut

Blademaster

Bladestorm

Cause a bladestorm of destructive force around the blademaster, rendering him immune to ability and dealing damage to nearby enemy.

Juggernaut

Blade Fury

Causes a bladestorm of destructive force around Juggernaut, rendering him immune to magic and dealing damage to nearby enemy units.

Even the description is likely copied from one to another, there's no doubt that Blademaster is an Arena Of Evolution version of Juggernaut. They are well-rounded 2 golds tanks with a powerful ultimate ability and two highly relevant race and class, which make them suitable for every army in any momment of the game.

#4. Skycrab - Lina

Skycrab

Laser Strike

Fires a beam of energy to a single enemy, dealing ability damage. Upon casting the ability, Skycrab gains 25% attack speed increase, up to 3 stacks.

Lina

Laguna Blade

Fires off a bolt of lightning at a single enemy unit, dealing massive damage. Grants Lina a stackable Fiery Soul bonus, increasing Lina's attack speed.

Despite her cost of 3 gold, Lina has worse stats than several 1 cost heroes. Her ultimate ability doesn’t make up for her very poor stats, which makes Lina one of the least played heroes in the game. Skycrab is on the other side when he is quite famous in the Red Tides battle that it's very usual to see him in any army. One of the major reason maybe because that Skycrab cost 1 coin less than Lina.

#5. Forest Rager - Tidehunter

Forest Rager

Earthen Spikes

Strikes enemies around, dealing ability damage and launching them to the air.

Tidehunter

Ravage

Slams the ground, causing tentacles to erupt in all directions, damaging and stunning all nearby enemy units.

Forest Rager and Tidehunter both are one of the 5 golds ultimate heroes in each game. Tidehunter’s Ravage ability completely dictates the outcome of late game fights. He is one of the only heroes in Auto Chess that should always be purchased and played whenever possible. Unfortunately Forest Rager is rarely seen in late game because his synergy is quite weak. It's not even make sense when you got 3 Immortals in the game despite of his good ultimate.

Auto Chess heroes's avatar and skill image source: https://qihl.gg