Hearts of Darkness (Merciless) is a secret stage in Growing Strange. It can be accessed randomly after completing An Elder Secret (Merciless). Completing this stage yields an Elder Catfruit Seed, with a very small chance of an Elder Catfruit.
- At the beginning, a Dark Otter and a Tackey will spawn. Nothing else will spawn until you hit the enemy base.
- When the enemy base reaches 99% HP, the base will spawn up to 2 Doge Darks, 3 Tackeys, 11 S.B.Ks, 5 Dark Otters and 1 Razorback. Once they are killed, nothing else will spawn.
If you plan on completing this stage whenever it comes up, you need to have Bombercat, Rodeo Cat or something similar in the lineup; that, and someone good forcrowd controll or damage are all that's needed specifically for this stage; as for the Tackeys, you can either lure everyone else close to your base by isolating your first bunch of units, stall them near the base while the Tackeys approach and then kill Razorback ASAP or you can use the lenght of the stage to "tank" the pushback caused by tackey and kill Razorback afterwards.
Once Razorback is dead, you have basically won.