The Last Chance is an item that is craftable in the Engender Mod.
Crafting[]

In order to make a Last Chance, the player needs four Blaze Powder, one Blaze Rod, one Feather, and a Totem of Undying, and they need to place them as seen in the picture in a Crafting Table.
Usage[]
Right clicking on any Engender mob that is not a tier 6 mob will consume the Last Chance and it gives the mob an extra life, functioning similarly to a Totem of Undying, just without the buffs. If a mob is killed after having a Last Chance used on it, they are effected with the Glowing effect and are brought back to life with one health left.