THE ELEMENTS
In my world, the four elements affect the use of magic in strange and often inexplicable ways. With the right power, you can cast spells to manipulate them, but if you leave out the smallest detail, they will backfire. As part of the original structure of the world, they are powerful, irresistible and unpredictable. Handle with extreme care, or suffer the consequences.

EARTH
The most solid and predictable of all elements, but also the hardest to manipulate. This includes soil, mountains, heavy vegetation (such as a forest) all kinds of minerals, gemstones and rocks. Like all the elements, it works the strongest when you are completely surrounded by it. It affects memories and perception of time. For example, it is very easy to get lost in a thick forest or in any type of tunnel. Also, it may see like you have been there for hours or years when it was really days or minutes. It is often hard to remember things about the Haethor, the race most associated with Earth. Those who wish to forget their past go to work in the mines. You can manipulate Earth by casting spells to make the people who enter unable to remember certain things. This is especially useful if you want to trap someone who has powerful magic. You can also make the Earth have a certain effect on those who mess with it; you could cast a spell on an entire forest, and make the occupants fall into an unbreachable sleep for hundreds of years.

AIR
The least predictable of all elements, but also the easiest to manipulate. This includes still air, wind, and some kinds of storms. It affects emotions, primarily. For example, if you are caught in a storm with high winds, certain emotions will be exaggerated, or you may experience sudden and extreme mood swings. The Raechal, who usually live on windy plains, have quick tempers and fiery emotions as a result. The Dragonriders are affected by this as well, but not as much. You can manipulate Air by casting spells to emphasize certain emotions. This is especially useful if you want to, say, discourage an army or energize someone to reach a certain goal.

WATER
One of the steadiest elements, Water is moderately predictable but almost impossible to control. This includes streams, lakes, oceans, clouds, rain, and, to a minor degree, heavy humidity. It is one of the elements with the strongest connection to pure magic. It affects mental connections of any sort, from telepathy to energy transfers. All connections but the strongest are severed by Water if the person is completely immersed in it. Rain and other weaker forms of the element produce static, of sorts. For this reason, the Sivanis, the race most connected to Water, have difficult connecting mentally. You can manipulate water by casting spells to interfere with certain connections, but only if you are very strong.

FIRE
Fire is the wildest of all elements. It will devour everything within reach, including you, if you let it. It can be controlled, but only if you know it well. This includes Fire in all stages, from ember to spark to flame to bonfire. It is the second element with a strong connection to pure magic. Fire affects enchantments exclusively. If exposed to even the most powerful enchantment for enough time, it will eventually dissolve it. Tulirans, the race most closely associated with fire, are hard to enchant unless you can taint them over a period of time. There is no known way to manipulate Fire with magic.

QUINTOR
Sometimes referred to as the fifth element, Quintor is a name derived from a word that means five. He is the God of my world, and is said to hold all the elements under His control. Under His command are all those who have given their lives to Him. His enemy is Cae’ach, who rebelled against His rule at the Beginning and slaughtered thousands of His closest followers. At times for the people, it feels like everything, even the elements, are against them, but Quintor holds it all in the palm of His hand and will until the End.

Are there any spells that involve the use of more than one element?

That's what HW is for.

I like that you include forests in the Earth element. I like the forces you attach to each of the elements, you did a very good job.