Innermost energon

Innermost energon is a Transformer's "core reserve" of power. It is extremely potent.

Fiction

IDW Comics continuity

When his fellow Duobot Ore was killed, Shock marked his passing in traditional form, with a vial of innermost energon along with some poetical remarks. Liars, A to D Part 3: The Chaos of Warm Things

Krok's band of Decepticon Scavengers hoped to find some innermost energon among the many scattered corpses on the battlefield world of Clemency. Krok commented that just half a gallon would be enough to power their ship, the Weak Anthropic Principle, for months. Rules of Disengagement After Flywheels was killed by the D.J.D., the survivors of the group speculated that there might be enough innermost energon for a sip each. Scavengers (Part 2): Who's Afraid of the DJD?