Anamnesis of the Blade
Orna
Rank: A
Type: Anti-Unit
Orna, Tethra's blade, which is always with Tethra when he is summoned. It is said to have spoken to Ogma after Tethra's death, and 'recounted all it had done' to him when it was unsheathed. This is only partially accurate.
When this Noble Phantasm activated, Orna 'recounts all it has done': Drawing the blade unleashes the coalescence of every single attack ever performed with the sword, even those from after Tethra's death, at the same time. Thus, to be struck by this sword is to be struck by 'every strike remembered by the sword' in the same instant, resulting in the target being struck thousands of times at once in thousands of ways.
This is not 'one enormous combined attack', however, but thousands of overlapping single attacks. This allows it to essentially be an instant kill attack on most enemies, as countless instantly fatal wounds are inflicted at once. This blade, which has even slain monsters and gods, is capable of striking down nearly any foe if used correctly, as the 'deeds' it recalls are not simply literal. For instance, if the blade had been used in the past to "kill a dragon with a stab to the heart", that strike is remembered as a "stab to the heart that kills dragons", resulting in any dragon hit by the blade being killed instantly with a strike to the heart.
However, hypothetically, if somebody is capable of surviving every one of the attacks remembered by Orna individually, they will survive. In the example above with the dragon, for instance, if the dragon is struck but does not have a heart to stab, they will not die (assuming that is the only strike remembered by the blade capable of killing that individual dragon, of course).
This Noble Phantasm is not just offensive, but defensive, as the 'deeds' Orna recalls are not only attacks. Blocks, parries, etc. are also kept in its memory, allowing it to stop any attack it has stopped before. As such, all but the most unique of sword strikes and spear blows are able to be easily defended against by Tethra, and more.
The legacy of Orna as "a sword that carried on after its owner died" manifests as well, in that it will remain even if Tethra the Servant is destroyed, and can be used by any strong enough to pay the mana cost.
The Cattle of Tethra
Each-Uisce
Rank: B
Type: Anti-Army
Tethra was a being of the deep, of the more magical abyss of the Ocean past. During his life as a Fomorian king, he had control of his flock of 'cattle': Vicious, Phantasmal sharks.
Upon the release of this Noble Phantasm, dozens of enormous sharks are called forth from the Reverse Side of the World, answering the call of their master even all these years later. They can only manifest in water, limiting the usefulness of this Noble Phantasm on land, but in their element they are deadly enough to tear apart most any foe Tethra faces.
This Noble Phantasm's mana cost is quite low: The sharks are summoned from the Reverse Side of the World and answer Tethra's summons simply because 'he is their King', and are not manifested by Tethra himself. Thus, the only work Tethra must do is 'make right the conditions of the water', to what it was in the days of his life, so that the Each-Uisce are able to comfortably act in the mortal realm.
Once the sharks have had their fill, they return home. As Tethra's Noble Phantasm is not manifesting them, only compelling them to come to our world, Tethra's death will not cause the sharks to leave, similar to how Orna remains after his demise. However, they may simply leave of their own accord once their master is gone, should nobody have done anything to anger them.