2. Get 'a Viridian Archer's patch' from the mob 'a Viridian Military, Archery Division recruiter'. You can find the recruiter in Xaventry, or in Tellerium (he wanders).
3. Get a spade and a pick axe.
4. Now you can head to the hydra's den.
5. Walk the dungeon, you'll find some marble pylons blocking your way. To get rid of the pylons, you need to kill the hermit crabs, and then turn marble squares in the Tunnel Full of Waste.
6. Now you must have the fire archer join your formation. And have him uncover/open the door to the xorn-hydra baby.
The player carrying the Viridian Archer's patch (should be form leader) must head to the room named Marble Cell. The player must enter the room alone for the archer to join. And must have the patch in his/her inventory.
7. Lead the archer to the room down from the safe at the entrance. He'll speak, then he'll uncover and open the down to the xorn-hydra baby.
Now you have to kill the newborn xorn-hydra crossbreed (baby), who drops the key to the menacing hydra (mother).
Once it dies, be sure you loot the key from its corpse.
8. Finally, have the archer kill the menacing hydra (mother) to get the mark.
Head to the room named Hydra's Den.
Search and you'll find a locked down. Unlock it + open it.
The goal here will be to get the archer to tank vs the mother, as he has massive hp.
Once the hydra dies, everyone in the form meeting the personality requirement gets the Mark Of Asceticism.