From LSWiki

Class: Physical Conditioning Skills

Attribute: Constitution
Pedagogy: Physical Training
Practitioner Term: Possessor of Hardiness

This skill represents one's physical toughness, the basic ability to withstand damage and injury and continue functioning.  The
higher this skill, the more one's physical durability -- hit points -- will exceed that which anyone of the same level of health
and constitution would possess.  Hardiness training past the levels of one's basic constitution has less effect.

Development Information: The hardiness skill was created by Chaos and is maintained by Lost Souls; the source code was last updated
Thu Jan 10 02:12:24 2013.

See Also: supernal durability

Trainers

the Green Chapel: Bercilak (I don't think he trains this anymore. it isn't in his list trigger.)
Wandering: Damon
Obsidia: Goth
Losthaven: Pryderi
Losthaven Arena: Raelan Jax
Association required:
Ghaunadaur: Ralgor
Losthaven Guard: Durit Kolbad
Maidens of the Spear: Sulin
Sodality of the Nine-Spoked Wheel: Grendal
Synodia Lykouros: Karth the Elder
Guild required:
Aisenshi: Musashi
Battleragers: Borulien
Brute Squad: Fezzik
Coven: Lynda Xenetha
Elflords: Celeborn
Hawkmen: Katar
Knights of the Round Table: Sir Lancelot
Nizari: Hasan Wanders
Ordo Ignis Aeternis: Iklam wanders Northlands
Shapeshifters Maramar
Verynvelyrae: Sirinil
zetesai: Linp
Quest required