Elidnis has two copies of each card listed below:
7ah 7ah 7ah 7ah 7ah 7ah 7ai 7ai 7ak 7al 7am 7am 7am 7am 7am 7gk 7gk 7gk 7gk 7gk 7gk 7gk 7gk 7gk 7gk 7gm 7gm 7gm 7gn 7gn 7gn 7gn 7gn 7gu 7gu 7gu 7gv 7gv 7gv 808 808 808 808 808 808 808 80b 80b 80b 80b 80b 80f 80f 80f 80h 80h 8pn
Permanent Control: None
Aether/Water Deck with fast boostable creatures that you can't kill. Bring a lot of Sundials, shields or other monster control. Not much apparent permanent or monster control other than the non-lethal congeal, so play your stuff with impunity.
Elidnis is most known for her immortal forest spectres which are nigh impossible to kill and can generate terrifying amounts of damage. One of the cards you can use to directly counter these immortal boostable critters is the thorn / spine carapace which has a high chance of inflicting any creature that attacks you with poison. However to use this tactic, you have to be able to survive the attacks with some serious healing. You can significantly weaken these guys with the rare weapon Eternity, this combined with Ottys can do some considerable damage to their strategy. The other tactics of fire walls or aflatoxins don't tend too work well since neither will deal damage fast enough to ever kill these immortal pumpable critters. With help from Shards of Wisdom, you can use them on the immortal Spectres and use a reflective shield for a good counter the Elidnes can't remove, only improve.
Without a means to remove her immortal critters you are left with simply having to survive until you can manage to kill Elidnis. This can be tricky since it is quite common to see four or five critters sitting in front of you that are capable of killing you outright in a single turn. Bone walls can be an effective counter here since Elidnis rarely has a large number of creatures. Using some form of continual creature generation (graveyards, elite queens, pharaoh, pheonix) and something to eat them you can cannibalize your own critters to keep feeding your wall to make it an endless barrier.
A pillar control deck will work wonderfully here, if you can deny Elidnis of her water and aether quantums, you will eliminate most of the creatures she can play, the only real cards after that she can play are her forest spirits (without growth they are very easy to deal with) black holes will deny Elidnis quanta, while restoring your own health. You could use armagios if you were Earth-Gravity to delay the forest spectres for a couple of turns. Aether wont work, despite it being effective against her creatures (phase shields), the empathy bonds and heals she has will keep healing her, while her spirit grow to near-ludicrous levels. Firefly Queen decks are a no-go, as while you may be able to set up, the ulitharids can counter their skills. Plus, you are always taking poison damage, while the forest spectres quickly turn into giants and crush you.
If you have a few Pulverizers on-hand, bringing Elidnis down is not really complicated with an un-upgraded Gravity/Earth creature health deck. Use 6 Plate Armors, 6 Basilisk Bloods, and 6 Gravity Shields to block nearly all inbound damage (her Dragons and upgraded Spectres are automatically blocked). Then use your Pulverizers to remove her Bonds and Staff and Towers at will. Add 8 or more Dragons to your own deck to apply damage. Note, you won't want to play with any units under 6 health, as Elidnis can Parallel them and you'll have to burn another Armor or Blood. A few Stone Skins and a full 60 cards should round out your deck to ensure you'll be around long enough for your oft-frozen Dragons to finish her off.