The Forest set (mostly appears in Tier 1-2):
Helm - Visage of Endless Voices: Restores 1 health to all your Forest creatures at the end of each turn.
Mantle - Sylvan Plates: Gives 2 Golden Runes every 2 turns in battle.
Weapon1 - Wooden Staff: Forest creatures played on your first turn have +1 health.
Weapon2 - Venomous Staff: Your Forest creatures have Poison.
Armor - Sylvan Tunic: Equip together with Sylvan Cloak and Sylvan Plates to give +3 attack to your Forest creatures.
Ring1 - Ring of the Serpent: Your Forest creatures cost 2 Golden Runes less to summon.
Ring2 - Shuffle a Herb spell into your deck. (Herb: 0 cost Forest spell, heals 2 to a single creature)
Cloak - Sylvan Cloak:Shuffle a Sapling creature into your deck. (Sapling: 0/0 cost Forest creature, 1/1)
Boots - Greaves of Leaves: When you play your first Forest card in a Battle, draw a card.

The Ice set (mostly appears in Tier 2-3):
Helm - Gaze of Thunders: Shuffle 2 Lightning cards into your deck. (Lightning: 14 cost Ice spell, 8 damage to a single target, 3 more damage for future electric spells, draw a card)
Mantle - Frozen Shoulderguards: Applies Defense on your first summoned creature. Does not count as a spell. (Defense effect: Target allied creature is immune to the next attack)
Weapon - Spiritstaff: When you first Ice creature dies, summon an Ice Spirit in its stead. (Ice Spirit: Ice creature, 2/2, Frosbite 1)
Armor - Vindicator of Tears: Equip together with Aeris Cape and Treads of Grace to give +8 health to your Ice Creatures.
Ring - Frost Ring: +1 Frostbite for all your creatures with this skill.
Cloak - Aeris Cape: Your Ice creatures have +1 health.
Boots - Treads of Grace: Whenever you play an Ice spell, gain +1 Soul Orbs in that battle.

The Corrupted set (mostly appears in Tier 3-4):
Helm - Corrupted Helmet: When an enemy infested with Corruption dies, another random enemy inherits the infestation.
Mantle - Keeper of Blight: When you infest an enemy with Corruption, the corruption counter starts at 5 instead of 1.
Weapon - Crystal Staff: Shuffle a Corrupted Blast spell into your deck. (Corrupted Blast: 10 cost Corrupted spell, deal 3 damage to all creatures except Corrupted ones)
Armor - Robe of Malediction: When an allied creature dies, deal 2 damage to a random enemy.
Ring - Ring of Decadence: Equip together with Robe of Malediction and Corrupted Helmet to reduce the cost of all Corrupted cards by 7 Golden Runes.
Cloak - Cape of Blight: When you summon a Corrupted creature, deal 2 damage to all creatues except Corrupted ones.
Boots - Hollow Feet of Twilight: Gain 12 Golden Runes and 2 Soul Orbs when you play a Corrupted card.

The Fire set (mostly appears in Tier 4-5, you can get two pieces as special quest rewards):
Helm - Crown of Firesight: Shuffle a Book of Fire into your deck. (Book of Fire: 8 cost Fire spell, look at 2 fire spells, choose one to draw; note that the spells are random, not from your own deck).
Mantle - Ignis Plates: Your Fire creatures have +10/+10.
Weapon - Blazing Fire Staff: Whenever you summon a Fire creature, cast a Firestorm on a random enemy. (Firestorm: Fire spell, deal 10 damage)
Armor - Armor of Burning Damnation: All your creatures have Fire Damage. Note: Applies to all creatures, not just Fire ones.
Ring - Ring of the Burning God: Your Fire creatures have +1/+1.
Cloak - Mantle of Wrath: When your first Fire creature dies, summon a Fire Wraith in its stead. (Fire Wraith: Fire creature, 7/5, has Fire Damage).
Boots - Infernal Greatboots: Whenever you play a Fire creature or spell, draw a card.

Miscellaneous - Common:
Helm - Mask of Souls: Your first creature in battle does not cost Soul Orbs, but the rest cost +1 Soul Orbs.
Mantle - Plates of Light: Restores 2 health to all your Neutral creatures at the end of each turn. Note: Only heals up to the original health value, if the creature's health is boosted, it will not be healed.
Cloak - Nightcape: Nighttime heals your creatures instead of dealing damage to them.

Miscellaneous - Uncommon:
Weapon - Redwood Cane: All your creatures have +4/+4.
Ring - Frozen Heart Ring: -4 Frostbite for all enemies with this skill.

Miscellaneous - Rare:
Ring - Seal of Fury: Whenever you draw a card, deal 4 damage to a random enemy.

Miscellaneous - Epic:
Ring - Signet of Decay: Enemy Corrupted creatures are paralyzed on their first turn. Note: Also applies to Corrupted creatures which appear later due to abilities.
Ring - Ring of Wealth: Gives 20 Golden Runes every turn in battle.
Boots - Steel Walkers: All your creatures cost 1 less Soul Orb to summon.
Boots - Boots of Haste: When your hand is empty, draw 4 cards. Triggers once in each battle.