Cudgel of Certainty is a fan made Legendary item.
Recipe
Philosopher's Stone (700g)
Chain Vest (720g)- 800g
Strategy
This item may be useful on supports with skill-shot based lane partners like Ezreal or Caitlyn, or on supports like Blitzcrank and Nidalee. I believe that it is not OP, as you still have to actually make a skillshot hit. It only gives an advantage, which in turn is balanced by its cost, for the said support may have to choose to build this early for early game dominance but risk not buying enough wards or a Sightstone or build this late for the retained gp10 and regen capabilities but less worth for the active.