The difficulty of this quest varies greatly depending on how prepared you are to face the hazards it presents, and since many of those preparations require materials from the Great Girros, the first attempt (or first few attempts, really) could be quite a chore.

There are a variety of nuisances you’ll have to deal with concerning the Great Girros. It dwells in the depths of the Rotten Vale, where nauseous gasses will continually sap your health. This can be endured well enough with a combination of fighting in areas where the mist dangerous (luring the Great Girros to these areas when possible), or by just enduring and paying extra close attention to your health. Failing all of those, you can craft some Hornetaur Mail, which has the Effluvial Expert skill. This skill will eliminate the toxin damage.

The second, more troublesome issue involves the Great Girros itself, as it can inflict paralysis and thunder blight, with the former being of especial concern, as it can leave you helpless for quite a while. The only counter to this (aside from the unhelpful advice to avoid its bites) is wearing armor with the Paralysis Resistance skill. One rank reduces the duration of paralysis by 30%, two by 60% and three grant complete immunity. Sadly, the only armor you’ll likely be able to craft with this property on it is the Vespoid Coil (Vespoid set belt). It’ll help, but a 30% reduction in paralysis time is nowhere near sufficient. The others - Girros Mail and the Paralysis Charm - both require Great Girros Hide, among other Great Girros part, so you obviously can’t craft them until after the Great Girros hunt has been completed… perhaps several times.

Lastly, the Great Girros is usually attended by less Girros. They do little damage on their own, but they can also paralyze you, and while they’ll flee if a few are killed, they respawn quickly enough, and survivors will return in time, making them a persistent nuisance you’ll have to attend to.

With all the preparation out of the way (what of it you can do, anyways) it’s time to face the Great Girros. Travel to the Rotten Vale and descend to the middle layer, where you’ll usually find the Great Girros (almost always attended by his pack of lesser Girros) in AREAS 6 - 9, many of which, of course, are covered in toxic mist. The lesser Girros should be dealt with first any time they’re around, and with melee weapons with a wide attack radius or area of effect, they can often be put to flight incidentally, while focusing on the Great Girros. Their constant bites and leaps can contribute greatly to your misery, especially if you end up paralyzed.

As for the Great Girros itself, it resembles the Great Jagras from the Ancient Forest in general body shape, being a quadrupedal lizard. The Great Girros doesn’t devour prey whole, instead relying on paralyzing bites and projectile spit. If you do get paralyzed, it’s fond of following up with an awkward flop-roll attack which does a fair bit of damage. Indeed, without the constant damage caused by toxin, or the ability to take advantage of a paralyzed foe, the Great Girros isn’t too dynamic of a foe. Just watch out for the Odogaron, which dwells further below, but isn’t above making an appearance in this quest - it’s a more fearsome foe.

The Great Girros’ lair in on a ledge in AREA 7, and to drive it to seek shelter there faster, strike its head, which receives the most damage. Its front legs and tail are fine secondary targets, and all of them are breakable, with the tail being severable. The Great Girros is weak to water, resistant to thunder, strong against Paralysis and weak to Sleep.