Hello to the Social Empires wiki, TheFinalPhase here.
For reference, I like using the word 'Fodder' for Soul Mixer components.
During my time back, I've been experimenting with the Soul Mixer- just like about everyone else- but some things I've noticed may seem good to know. There seems to be a small pool of 'Strong' Soul Mixer fodder that can make some strong units when mixed. Remember- the outcomes are not guranteed and you may need to reenter the units multiple times in order to get your desired units.
Notable Fodder, avaliable via Barracks from the past or now
Orc Battering Ram - It's declared a strong unit for it's whopping 500 attack and 5,000 health, and therefore is a good fodder. When combined with some other decently strong units, soul mixing Extreme dragons becomes common, and no dragons even need to be used in the process. It's optional to, and can possibly come up with the same outcome.
Antimatter Golem - This unit's barracks are currently avaliable for 42 cash, and it's worth it if you have the cash on spare. This unit makes an excellent Soul Mixer fodder. It's good on it's own, as it's basically a buffed-up Vulcano Golem. It's price for building it from the barracks is 16,000 gold and 32,000 food; but two of them in the soul mixer can easily create a powerful dragon.
Hydros Titan - From a long whiles ago, the Hydro Barracks was avaliable to be built. Although this unit is minisculed from recent units, this unit is still a good fodder. Combine this unit with either of the above units and a powerful unit may appear.
Notable Fodder, avaliable via Cash Offers, Soul Mixing or Tournament Winnings
Galaxy Dragon - This unit is a strong unit that, when combined with other notable fodder dragons, will provide you with a strong unit, often Extreme dragons.
Rainbow Dragon - All the colors of the rainbow reside within this unit. Acts the same as Galaxy Dragon, except from what I've seen it's a bit more common to Soul Mix.
Dynasty Dragon - A powerful unit, and when soul mixed with proper units will create an even more powerful outcome.
Golden Dynasty Dragon - A more powerful version of Dynasty Dragon.
Any Above Dragon Ridden - Dragon Riders make for an extra bonus in the Soul Mixer. When a dragon is soul mixed with a rider, the outcome will be more powerful than if the dragon did not have a rider.
Units that are recomended against Soul Mixing
Extreme Dragons - Here's where opinions part. Some people gladly soul mix Extremes because they have pleanty at their disposal. However, if mixed unproperly you can end up with a unit far weaker than the Extreme you put in. You can use them to Soul Mix, and if properly mixed they can make something stronger than them; but there is not very much that the Soul Mixer can offer above Extremes and the 3-headed Primal Dragon.
2-headed Dragon and Epic 2-headed Dragon - The attack delay on these two two-headed dragons kills thier potiantal. When I was experimenting with them in the Soul Mixer, nothing good came up; even when it was put up next to any of the notable fodders I listed.
Please note, these are my experiences only. The outcome to others may differ from mines.