Welsh story has no unmistakable traces; here the hero (Llew) is invulnerable except with a certain weapon and in a certain position. This magic weapon might be perhaps a remnant of an external soul motive: in Irish story Cúrói's sword is a necessary instrument for destroying Cúrói's soul, because it is his own sword. It would be only natural then if the slaying power of the sword were explained, not as a possession of the hero who is to be killed, but as a supernatural quality of the sword itself, and so it is possible that in this way the story-teller came to evolve the idea of a magical weapon. There is, however, still another motive which does not occur in the External Soul theme: the hero can be slain only under certain conditions; otherwise he is deathless: Llew cannot be killed either within a house or without; he cannot be slain on horseback or on foot (R.B. 705, W.B. fo. 196 d: Ny ellir vy llad i y mywn ty . . . ny ellir allan, ny ellir vy llad ar varch ny ellir ar vyn troed). The words are a formula intended to mean: he cannot be killed at all and a situation is invented which satisfies this formula. This motive that somebody is cunning enough to avoid difficulties comprised in some regulation intended to be incapable of being performed is common enough. A lord gives an order to his peasant subject that his (i.e. the peasant's) daughter shall come to him neither riding nor going (on foot); the daughter comes walking on one foot and the other leg on the back of a goat. (It is very significant that Llew has to put one foot upon a buck.)
Another example of this motive we find in the Mahābhārata (18. 43. 2434): Indra made friends with Namuci, and promised not to slay him with wet nor dry, in the day nor in the night. One day Indra beheld a fog, and cut off the head of Namuci with foam of water. We see that in such stories only the negative form is given; the method of evading the formula is to be found by the opponent, and so I suppose that originally Llew himself said only the
