"Kikimore queens' unique nervous systems inspired renegade mages to develop this strong mutagenic potion. The potion causes changes in the ventral cavity and also prompts production of mutated digestive enzymes. Broad use of the potion was curtailed due to the scarcity of its core ingredient."
When imbibed, Kikimore's Ire, a mutagenic potion, provides access to a special enhancement of the Stamina attribute; this upgrade allows a witcher to consume raw monster parts, restoring lost Vitality, but also raising his level of body Toxicity.
Note: Despite the item's text stating that consumption "Allows you to buy the Mutation Stamina upgrade", the attribute is unlocked immediately and you do not need to spend a talent point.