In From the Ashes, Sheidheda tells Russell Lightbourne in Trigedasleng that he is now him as the Dark Commander kills the Prime.

In False Gods, while burying the Flame alongside Abby Griffin's ring, Gaia states that "their fight is over" in Trigedasleng.

In Welcome to Bardo, after realizing that Sheidheda is possessing Russell Lightbourne's body, Indra addresses him in Trig, stating that there is a spider on the Dark Commander's shoulder. Realizing that she knows who he really is, Sheidheda responds in kind that its too bad she can't kill him. During their subsequent confrontation, part of it is in Trig.

In Anaconda, Niylah asks Clarke who Bill Cadogan is in Trig and she explains in the same language that his cult built the Second Dawn Bunker. To their surprise, Cadogan is able to understand them, though he requests that they speak slower since it has been so long for him. As the language has survived, Cadogan asks if his daughter Callie has survived in the key: the Flame. Cadogan reveals that Callie created Trigedasleng as a child and suspects that Clarke's knowledge of the language means that Callie has survived inside of the Flame.

In a flashback, Callie says "your fight is over" in Trig after Baltimore is destroyed by a nuclear missile. She later tells Becca Franko that she had learned Latin when she was 10 to help create the language.

In The Flock, after massacring the Faithful, Sheidheda orders that the door be opened in Trig and declares that "my fight is just beginning."

In A Little Sacrifice, after being left with Cadogan, Niylah comments on the awkwardness of the situation in Trig. Understanding her comment, Cadogan asks after his daughter and Niylah tells him what she knows of Callie's ultimate fate from Grounder legend.

In Blood Giant, Indra and Sheidheda use Trig to communicate while tied up together so as to ensure that the Disciples guarding them won't understand their conversation. After noticing a cloaked Disciple sneaking up behind Indra, the Dark Commander yells out a warning in Trig, saving her life. In Indra's hallucinations of her mother due to the Red Sun Eclipse, she and Sheidheda speak in Trig. After deciding not to kill Sheidheda but to let him die, Indra states that "your fight is over" in Trig. During her final argument with Bellamy Blake, Clarke uses Trig for the most important parts of it so that the other Disciples won't understand exactly what she's arguing with Bellamy about.

In A Sort of Homecoming, after defeating the Dark Commander with Gaia's help, Indra tells him that "your fight is over". However, as Indra moves to kill him, Sheiheda replies "not today" in English and stabs himself with the Disciple locator tagging device, escaping through the Anomaly.