Veelas, Sirens, Dryads, Nymphs, Rusalki, Lake Maidens, Glaistigs and many more, all-female races one and all, have united in the face of muggles’ expansion and the wizards’ secrecy. They manipulate, lobby and subvert, trying to ensure that their races not only survive and continue into the next generation, but also thrive.
To achieve that, they need a steady supply of men of character, integrity and strength. Magical power is preferable too. In every magical school there are scouts on the lookout for young men that look promising.
Harry Potter seems to be a promising candidate, despite his unfortunate upbringing. The Tri-Wizard tournament was meant to be used as a chance to establish contact with him. The delegations from Beauxbatons and Durmstrang include young, promising women, chosen for their desirable attributes and willingness to enter into a relationship with the young man, to convert him to the cause, so to speak.
His entry into the competition complicates matters, a sure sign of somebody else having designs on Harry Potter. And the situation is even more complicated by the fact that he has eyes for the Ravenclaw seeker Cho Chang.