I'm pretty much convinced by Vernam Hull's argument that "deiltre =
druid gods" is an error. It makes perfect sense to read this line,
which can be read on line at ISOS*, exactly as it is written:
"acht nis·leig in deiltre .i. in dé draideachta i tir"
= but the deiltre, i.e. the magical smoke/vapor/steam/haze, did not
allow them to land
* http://www.isos.dias.ie/ > LS 23 P 2 (Leabhar Mór Leacáin) f. 191v a
In other words, the druids raised a mist/fog/smoke screen that obscured
the shore and caused the fleet to lose its way. The topos of the "ceo
draíochta", the "magic mist", is quite common in our literature. It's
also normal in the literature for the druids, rather than their gods,
to attack their foes directly with their magical powers.