Týr

Týr is the god who pays for a contract with his body. In Snorri's Gylfaginning the gods want to bind the wolf Fenrir with the dwarf-made cord Gleipnir, and the wolf, suspecting a trick, agrees only if one of them will lay a hand in his mouth as a pledge. Only Týr does it. When the cord holds and the wolf understands he has been deceived, he bites the hand off. The gods laugh; Týr does not. What the scene turns on is not courage in battle but the breaking of a sworn undertaking, and the god of oaths is the one who pays for it.
That is why the older reading of Týr is legal rather than martial. A Roman-era inscription from Housesteads on Hadrian's Wall, set up by Frisian soldiers, is dedicated DEO MARTI THINCSO, to the god Mars of the Thing: the assembly where law was spoken. Read with the Norse evidence, it points to a god of the sworn assembly whom Romans matched to their own war-god, not a war-god as such.
His name is the deepest thing about him. Old Norse Týr goes back to Proto-Germanic *Tīwaz and beyond that to the Indo-European sky-god *dyēus, the same root that produced Zeus, Jupiter and Sanskrit Dyaus. In Old Norse the word had also worn down into the ordinary noun for 'god', which is why the plural tívar simply means 'the gods'. A name that means 'god' usually belongs to someone who was once the god, and many scholars read Týr as a sky-father displaced by Odin long before the Eddas were written.
The sources do not agree about him, and the entry keeps that open. Snorri makes him Odin's son; the Eddic poem Hymiskviða gives him the giant Hymir for a father. Sigrdrífumál puts him in the runic world, telling a warrior to cut victory-runes on the sword-hilt and name Týr twice, and the rune ᛏ carries his name. At Ragnarök he does not face the wolf he bound: he meets the hound Garmr, and each kills the other.