(Mistveil Retreat isn't a spell.)
At the beginning of your end step, if you didn't cast any spells this turn, Mistveil Retreat deals 1 damage to you.
,
: Tap target artifact with converted mana cost X or less.
, Pay 1 life, Sacrifice Mistveil Retreat: Search your library for a Plains or Island card and put it onto the battlefield, then shuffle your library.