Mordecai's emergency potion granting thirty seconds of near-invulnerable hyper-healing — usable only once every ten hours.
Mordecai's Special Brew is Mordecai's alchemical trump card, and Carl's last resort against the war god Grull in trainyard E. Drinking it triggers 'Gold-Standard' super-accelerated healing for thirty seconds — effectively near-invulnerability — but locks out any other potion for a punishing ten hours. Under its effect Carl is stomped flat by Grull's flaming horseshoe, has his back and pelvis shattered, and is bowled over by a rolling train car, healing from each catastrophic wound in real time until the timer runs out.
The potion Mordecai told him to keep for the worst possible moment, spent to outlast a god.
An emergency alchemical potion; its effect is a golden 'Gold-Standard' hyper-healing aura.
Mordecai's emergency near-invulnerability potion, the difference between Carl living and dying against Grull.
Also appears in books you've already read — spoiler-safe to their endings: