One of the Hearthstone game designers, Mike Donais, gave an insight into the development of the elementals for the upcoming "Journey to Un'Goro" expansion.

Not only is Un'Goro crater full of dinosaurs, it is also home to the dangerous elementals. During the development of “Journey to Un'Goro”, Blizzard not only designed new elementals, but also adapted previously published cards from previous expansions to the new mechanics. The following cards have been converted to elementals:

1. Water elemental
2. Anomalus
3. Ragnaros the Lord of Light
4. Spawn of light
5. Dust devil
6. Unleashed elemental
7. Fire Guard Destroyer
8. Rumbling elemental
9. Earth elemental
10. Fire elemental
11. Neptulon
12. Al'Akir the Wind Lord
13. Arcane Anomaly
14. Ice rage
15. Magma Waters
16. Frost elemental
17. Baron Geddon
18. Ragnaros the Firelord

This makes them valid targets for the new mechanics, which Mike Donais uses the example of the Steinwächter explained.

You conjure the Stone guardian, after you have played an elemental on the last turn, the battle cry is activated and summons two elementals (2/3) with mockery.

The legendary card Ozruk go one step further and get +5 life for each elemental you played on your last turn. So like Edwin VanCleef you can come across a really huge monster.

How did this new Hearthstone Elemental mechanic come about?

Based on the expansion The Black Rock, in which the interaction of different dragons was developed, each type of servant should, if possible, contribute something unique to the gameplay.

Dragons often get additional effects if you hold another dragon card in your hand. There are now complete deck types that focus on these synergy effects, such as dragon priests.

During the conception of “Reise nach Un'Goro”, the development team developed, tested, discarded or improved 10 different ideas. At the end there is the mechanics that players will find in the new cards from April.

Failed ideas that didn't make it into a trip to Un'Goro

Mike Donais also describes some ideas that did not work due to various problems:

1. Elementals get a bonus if you cast a spell this turn.
2. Elementals receive a bonus if the last card you played was an elemental.
3. Elementals receive a bonus if the last servant you played was an elemental.
4. Elementals get a bonus if you control another elemental.
5. "Elemental" was both a servant type and a wizard type.
6. You gain elemental charge and can use it to power up your elementals.

In addition to the new concept, there are also other new Elemental cards, for example this Fire devil: Get an Elemental (1/2) in your hand or the Flame geyser: Deals 2 damage. Get an Elemental (1/2) in your hand.

With the Legendary Card Pyros there is also a fresh concept. Pyros starts as a 2/2 servant, when you die it returns as a 6/6 servant to your hand. In the next reincarnation he will even be reborn as a 10/10 servant!

Journey to Un'Goro will feature approximately 25 new elementals, mostly assigned to mages and shamans. Both classes that traditionally use elemental magic, but there will also be neutral elementals so that each class can experiment with the mechanics.

The Hearthstone expansion will be released in April, there is no official date from developer Blizzard yet. However, there are indications that point to April 6th, because on this day the Amazon Hearthstone Coin pre-order campaign for "Journey to Un'Goro" ends.