Elden Ring centers around the Greater Will, which spreads its Grace to the Lands Between through the Erdtree. The Erdtree might be the most famous plant in the Lands Between, but Miquella seeks to create a new great tree as a source of power to bless the people without the influence of the Greater Will, despite having been chosen by the Greater Will as an Empyrean. However, both of these great trees might have some parasitic qualities depending upon how they're viewed and what acts as their source of power. Yet only one of them is a true parasite upon further investigation.
[Warning: This article contains spoilers for Elden Ring.]
Elden Ring is an open-world RPG created with help from author George R.R. Martin that is set in the Lands Between, where the Greater Will's influence is the most dominant amongst the Outer Gods that have come in search of power. It is the Greater Will that sends the Elden Ring to the Lands Between, and it raises Marika to godhood so she can contain the Elden Ring as its vessel. However, life under the influence of the Greater Will isn't what all residents of the Lands Between desire, and many of them begin to grow disillusioned with the Greater Will and its Golden Order. The demigods, in particular, stray away from the Greater Will and seek their own paths and power in Elden Ring.
The Erdtree is a focal point of Elden Ring, bestowing Grace to the Tarnished. However, the Erdtree has not always been part of the Lands Between. The Erdtree is said to derive its power from the Elden Ring, but there are item descriptions that suggest the Elden Ring might not be its only source of power. Having stable sources of power is among the reasons that Miquella's Haligtree is not able to replace the Erdtree or free him and his sister from their curses as he had intended to do with its creation, since the Haligtree's source of power is forcibly removed from it before the events of Elden Ring begin.
The Connection Between The Crucible And The Erdtree
Understanding the Erdtree requires knowledge of the Lands Between before the Outer Gods, particularly the Greater Will, take an interest in it. Outer Gods that are seeking power would need to have a reason to choose the Lands Between as the place they seek to spread their influence. The Greater Will wouldn't put in the effort and send the Elden Ring to a land if it doesn't gain anything from controlling that land. What the Greater Will is likely after goes back to a point on the timeline before Elden Ring begins. The first hint at what the Greater Will wants is in the Aspects of the Crucible description, which says, "This is a manifestation of the Erdtree's primal vital energies - an aspect of the primordial crucible, where all life was once blended together." Any object or being capable of holding all life blended together would certainly be a target for the power-hungry Outer Gods.
If the Crucible is the primal energy of the Erdtree and where all life once blended together, then it has to contain an incredibly large amount of power. This connection also shows the Erdtree's parasitic nature because it needs to feed off of the energy of the Crucible, unable to survive without an external source of energy. Since the Crucible is where life blends together, it can be assumed that the second source of energy for the Erdtree is the souls of the dead who will tell the Tarnished that they are waiting to return to the Erdtree. The reach of the Erdtree's roots allow it to gather those souls easily, and allows it to spread the Greater Will's Grace through the Lands Between. Regardless of how the energy is used, it's gathered through parasitic means.
Miquella's Haligtree Is Meant To Make The Erdtree Obsolete
Like many of his half-siblings, Miquella has strayed away from following the Greater Will despite being chosen by it as a possible successor of the Elden Ring. Therefore, Miquella decides to create a great tree on his own in an attempt to replace the Erdtree and make it so that the citizens of the Lands Between don't need the Grace of the Greater Will. Miquella uses his own power to nurture the Haligtree, becoming its core in hopes that it will grow into a great tree that can rival the Erdtree, break his curse of eternal childhood, and free his twin sister Malenia from the curse of Scarlet Rot that eats away at her body.
While it might seem to be parasitic, the relationship between Miquella and his Haligtree is actually more symbiotic. In Elden Ring, Miquella's cocoon is the only form in which he's seen. Mohg, as someone obsessed with Miquella, cuts him out of the Haligtree and takes him away, and due to this, both the Haligtree and Miquella suffer, displaying their symbiotic relationship. The Haligtree is not a parasite, and it's unfortunate that its potential is never realized due to Mohg's actions. Since Miquella's status is unknown, if he's alive, it's possible that he might try to salvage the Haligtree, or he might start over if it can't be saved.
Between the two trees, the Erdtree is the true parasite. This fits the ongoing theme in Elden Ring that the Greater Will, despite being presented as a benevolent Outer God at first, is more vicious and controlling than it tries to make others believe. Because of the Greater Will's true nature, it isn't a surprise that Elden Ring's Age of Stars ending is the favorite among players since Ranni begins a new order of her own that won't directly interfere with the lives of those in the Lands Between in the way the Golden Order does. While there's enough information to deem the Erdtree as a parasite, the lack of information about the Greater Will makes its intentions unclear. The purpose of creating a parasitic tree that uses the power of the Crucible and the dead will only be revealed if FromSoftware adds DLC or creates other future content through an expansion or sequel for Elden Ring.
