If said in another way, rank 3 spells can be used with more than one life seed because of their increased complexity, while rank 2 spells can only be used with one life seed.
So if a cultivator at the second mortal coil manages to learn and use a rank 3 spell, they won't be able to use it to its full capabilities because they only have one life seed to use it.
So only a cultivator at the third mortal coil can bring out the full benefits of learning the more difficult rank 3 spell. Cultivators at the second mortal coil, no matter how intelligent and special they are, are better off just sticking with rank 2 spells.
The opposite is the case too. A foundation establishment cultivator who learns and uses a rank 2 spell will not be able to channel the power of all of their life seeds into the spell.
If a foundation establishment cultivator can't take advantage of their life seeds, their power will be stuck at 110, just like energy refining cultivators. The only advantage they will have over energy-refining cultivators will be their talents and the passive benefits of their foundation.
Only rank 3 spells possess enough complexity to accept and work with the multiple streams of energy coming from numerous life seeds at the same time without crashing. So foundation establishment cultivators should learn rank 3 spells, not rank 2 spells.
He doesn't need spells to show his full power. As a dual cultivator of body refining and energy refining, he can fight with his body. He can also use his foundation to unleash the power of lightning on his enemies.
His control of lightning and usage for offensive means doesn't require the assistance of spells. But it is undeniable that spells can be very useful in certain situations.
So he decided to peruse the list of spells available for those who cultivate the Everlasting Wood Art and the Divine Lightning Armament. As someone who possesses both the lightning and wood elements, he can learn spells of both groups.
After going through the lists, he chose the Lightning Angel spell, the Lightning Net spell, the Wood Burial spell, and the Wood Army spell. He chose both spells for their power.
There was the Wood Giant spell, which encapsulates its user in a giant wooden statue that could be controlled. There was also the Thunder Roar spell, which creates a sudden loud sound that can deafen people and even stun them.
There were many more spells like the Lightning Rope spell that binds foes, the Lightning Rain spell that causes lightning to fall from the sky like rain, the Thorny Forest spell, which creates a forest of spiked spears that can impale enemies, and the Wood Explosion spell, which turns wooden constructs like trees into bombs.
There was an endless number of spells. They were all enticing and tempting to learn. But he couldn't learn all of them. He just didn't have that much time on his hands.
He has to spend most of his time cultivating. If he is not cultivating, he will have to master the three very important techniques that he needs to master before rank 4.
These three rank 3 techniques are the two host techniques and the Life and Death Lightning Art. The three of them are way more important than any spell, so he should prioritize them over other spells. This is why he chose just four spells.
He picked those four spells not only because they are highly destructive but also because they possess some utility functions other than being destructive.
For example, the Lightning Angel spell encloses the user in a coat of energy that resembles an angel with wings made of lightning.
The Wood Giant and the Lightning Angel both have similar modes of operation. But he chose the Lightning Angel spell because nothing could match lightning in the aspect of destruction and speed. Especially not wood.
The angel that the Lightning Angel spell will turn the user into will possess enhanced speed, an energy barrier for protection, and energy attacks. So it has three functions in one.
Of those three functions, only one of them is for attacking. The other two can be used for evasive actions or escaping and for defensive actions.
This varied and abundant function of the Lightning Angel spell is not something unique to the spell. Every rank 3 spell is like that. They always have more than one function.
The extra potential utility of rank 3 spells is because of their higher complexity and because of the possession of the divine sense by foundation establishment cultivators.
The higher complexity of rank 3 spells means that they can be programmed to do more than one thing. And since foundation establishment cultivators have a lot of energy, there is enough energy to go around to use the extra functions of these spells.
Where the divine sense comes in is more tricky. The main effect of divine sense on spells is a more accurate means of control.
Because of the better control granted by the divine sense, spells can be used for things they weren't programmed to do, such as the Lightning Net spell, which was originally meant to be used as a method for area of attack but can be used as a defense by creating a small, compact lightning net to block an attack.
This boost from the divine sense is not limited to rank 3 spells. Rank 2 spells also gain benefits from the enhanced control. Unfortunately, the enhanced control can't make rank 2 spells match rank 3 spells in terms of versatility.
After making his choice, he left the library. When he got outside the library, he used the beast mark spell to call Roar to him.
The beast mark is something he implanted in Roar through the rank 3 Beast Link spell. Thanks to this rank 3 spell, he can communicate with Roar no matter where Roar is.