im not much experienced but i think there are three ways:

1.go to the (sinking feeling) quest,there is another but i cant remember the
name,WARNING:do NOT fight it if u have:
_weak armor and wepon
_not ready
_not enough items.
2.i think u have to go to lvl 5 quests(village cheif).
3.go to a level on glide quests,i dont no wich level

so there you go.
maybye there are other ways.
btw this is my first post EVA.

you fight the tigrex lvl 5 quests village cheif strong armor and wepon

Lvl 5 urgent quest chief the best armour is full rathian and best weapon eager cleaver