Trandgoth ,death serpent

Islandwalk
When Trandgoth ,death serpent enters the battlefield it enters with ten slumber counters
on it Whenever a land enters the battlefield
under your control remove a slumber counter
from Trandgoth ,death serpent if Trandgoth
,death serpent has slumber counters on it its
a land
{t}:add {g}{g}{u}{u} to your mana pool