The best evidence to date comes from three sources. These are two Trans Neptunian Objects that are in highly elliptical orbits that could have only gotten that way due to the influence of something massive in the outer reaches of the Kuiper Belt. The problem here is that these two object's orbits are the result of separate influences as both have entirely different orbital elements and the orbital planes are also different. The third piece of evidence is the fact of Uranus strange orientation to the ecliptic. The poles of Uranus point almost directly to the sun once every 41 years. Thus, the solar system either has two very massive TNOs, or these strange facts are the result of an aperiodic penetration of the solar system by rogue planet sized bodies that pass through once. Nibiru is a legend apparently inspired by ancient knowledge of this, or an observation of an object of this kind. There are no hard answers beyond this, but there is increasing support theoretically about the existence of rogue bodies in space ranging in size from the moon to several Jupiter masses. Based on recent calculations, at least 100 of such bodies exist within one light year of the solar system. Most of them would be small, a few the size of the earth to Neptune and one or two the size of Jupiter or bigger. They are out there and stand as the best contemporary proof of something like Nibiru.