The Radical Isotopes are elemental isotopes that usually are unable to exist in our reality, since they have a negative mass, which breaks every law of physics known to the sentient races of the universe. However, they originate from the Spirit of the Abyss's Pocket Universe and could be of help in defeating it. Agents of the Abyss have the isotopes in their bodies, as a result of being possessed or affiliated with the Abyss. When Agents of the Abyss are asked the question, "From the beginning, what are the ten radical isotopes?", they must answer and reveal themselves as Agents of the Abyss.