sorry for the double posting, here is my final analysis on how Slayer can pair up with each of the elements or how it can't:
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: mainly the holder of immaterial creatures, quint, and one of the most potent shields in the game, phase shield. It was said that Aether needed another non-immaterial creature that can stack some damage and have fairly decent survivability against damage CC, however, alongside Phase shield, Slayer can potentially act as a lock down card for decks without PC, and against decks with CC, Quintessence is all that is needed. Quinting is the main key for Slayer to virtually become one of the most powerful CC methods in the game.
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: A very potential damage stacker with Skyblitz and wyrms, also having an efficient shield called Wings, however, in nature Air usually lacks good CC tactics, one of their main CC is shockwave, and a good thunderstorm barrage. though not as powerful in CC as other elements. Adding Slayer to this Element would certainly make it very potent as a defensive and very offensive element, perhaps not a good option.
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: Very devious with its quanta steal and occultive cloak. Also an efficient duo element lock down with fractal, pest and Upped Eclipse. Adding Slayer here will automatically influence decks with eclipse and Slayer, to add to its attack and defense. not only that, I am not sure how Liquid shadow would impact with its use on Slayer.
question: In the case of adding Slayer to this element, Could Slayer absorb hp from creatures as well?
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: Death is more based on slow decay poison and now a days Skeleton spamming, especially with the new buff of Skull buckler. Adding Slayer into this element would certainly just boost its CC capabilities even higher alongside plague and skeleton shield.
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: Earth is mainly based on on average and high damage output but with defensive mechanisms on its creatures such as burrow. Implementing Slayer into this element would certainly be a good addition for an Effective CC device and addition to its mid range creature arsenal.
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: Entropy is based on random gambling and numerous effective CC devices such as mutation, paradox, antimatter, chaos bolt and pandemonium. I doubt Entropy needs another effective CC method since it already has a big arsenal of it.
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: A huge Damage stacker with Lava golems and virtually undying Phoenixes, also has a shield that already deals quite the damage against attacking creatures with Fire shield. Adding Slayer to this element may seriously create an even higher boost to its offensive capabilities as well as defensive united with Fire shield and Rain of Fire.
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: Deals with the damage attraction mechanism and momentum attack strategies, also a good defender against high attack - CC survivable creatures with gravity shield.
Due to the shield, I think implementing Slayer into this element would be a serious lock-down mechanism against opponent, while the high attack anti-CC strong creatures cannot harm you, destroy them at the same time with Slayer, Gravity force will become an ancient and terribly forgotten and useless tool. I doubt it needs to create a waste of a card.
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: Life has some serious healing potential with empathic bond and mitosis plus frogs and cockatrices. I doubt it needs such a powerful CC method when it already deals with it with healing and poison carapace.
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: The originally desired element for Slayer. Light has some serious potential with blessings and miracles, however it does lack direct CC methods is rather more focused on defense by direct healing via. Miracle and Healing flash. The only questionable thing with light is blessing used with Slayer, will this create an unstoppable rampaging CC insta-kill monster? despite it being able to be stopped with Gravity shield after a single blessing, it will still satisfy its thirst against the high attack creatures.
However, there is still one counter against Slayer, and that is Entropy's Anti-matter, If slayer is anti-mattered, it could possibly heal the opponents creatures fully and easily instead of damaging them, so there is a note there that can support Light on having this creature plus its lack of direct CC.
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: Time having the new cheap and average damage dealer Ghost of the past and having the stalling Eternity weapon, certainly does not need Direct CC included with its CC by stalling capabilities.
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: Water has one of the largest arsenal of creatures, however, most of those creatures need some effective Duo strategies in order to be used to their full potential.
but it does have some of the most powerful forms of CC devices such as Arctic squid, Frost shield, Freeze and Inundation, as well as a duo capability of freeze and air causing instant kills alongside the insta kill mechanic of Inundation.
I doubt That like, Entropy, it needs another powerful CC such as Slayer.
those are my notes on Slayer element syncs and capabilties.