Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)

Reach, trample

Nyxborn Hydra enters the battlefield with X +1/+1 counters on it.

Enchanted creature gets +1/+1 for each +1/+1 counter on Nyxborn Hydra and has reach and trample.