Yggdrasil

Yggdrasil was one of the Ragnarok, originating from the Ruin Gigas.

Appearance
Yggdrasil was an enormous tree, covered in dark red veins and with countless branches and roots. Skulls covered its trunk.

After assimilating many Drag-Rides, it incorporated them into its body. It had cannons within holes in its trunk and swords emerging from the tips of its branches.

Yggdrasil has a different appearance in the anime. It consisted of an single enormous skull with an open mouth, surrounded by branches or roots. It did not have red veins or Drag-Ride armaments.

Abilities
Though resembling a plant, Yggdrasil was capable of movement, using its roots to move around and its branches to attack. It attacked using its branches and any Drag-Ride armaments it had incorporated.

Consumption: Yggdrasil could consume both organic and inorganic matter. When it consumed living organisms, such as other Abyss, it took in their life energy. When it consumed Drag-Rides, it could incorporate their weapons into its body and use them to attack.

Ratatoskr: The seeds of Yggdrasil, which can be implanted into a host (either a living organism or a Drag-Ride) and will merge with their body. Hosts have an altered appearance (dark red veins, black eyes with gold pupils) and increased strength, regeneration and mental capabilities. This comes at the expense of increased life energy consumption, which will lead to death if all life energy is consumed. Upon death, a host's body crumbles into ash. Yggdrasil could control hosts of its seeds through sound waves. Hosts could choose to reject Yggdrasil's orders, but this caused intense fever and headaches, and it was impossible to reject orders if Yggdrasil focuses its strength. If a host attacked another Yggdrasil host, this was considered an even greater act of rebellion than rejecting an order and would kill them within several days.

Regeneration: Yggdrasil could rapidly regenerate from damage. This ability consumed life energy, preventing Yggdrasil from regenerating endlessly, but Yggdrasil could compensate for this weakness by consuming Abyss to steal their life energy.

High-Speed Reinforcement: When Yggdrasil was attacked, it developed resistance to the type of attack used against it and also increased its power and speed. It could develop resistance to a variety of attacks, such as gravity and freezing, but not to space-time distortions like those created by Nidhogg (presumably, this would also apply to Deus ex Machina's space compression). This ability also consumed Yggdrasil's life energy.

Trivia

 * Yggdrasil is a tree in Norse mythology that connects the nine worlds. Ratatoskr is a squirrel that runs up and down Yggdrasil to deliver messages.