Solerius Umbro, Eclipsed

Solerius can not be played unless any player is
more than double or less than half their starting
life total
When Solerius enters the battlefield, put X -1/-1 counters on each non-white creature you don't
control. Then you may gain life equal to the
number of creatures with -1/-1 counters on them
or put a creature card from your graveyard onto
the battlefield if its converted mana cost is less
than X