On My Mark is a Tier 4 Skill in Jack's The Hero of This Story skill tree.
Combining this skill with Jack's Cache will deploy three grenades, two from the Digi-Jacks and one using Jack's Cache stacks. Using any grenade that spawns a child grenade can create mayhem dealing significant damage over a wide area. Though because this gets hectic, the closer Jack is to the enemy, the more likely that person is to get killed from a grenade. Any kills from this can add stacks of Cache so use the free grenade first and then use On My Mark.
Another use is to equip a transfusion grenade so that health can be restored more rapidly. Again if three grenades are thrown at the same time they will all seek out enemies to drain health so Jack receives up to three times the normal regeneration.
- The Digi-Jacks don't always throw the grenade in the right direction and instead throw the grenade where they are currently aiming.