His is the spear that pierces the stone. Hers is the blade that divides the sea.
His is the spear that pierces the stone.
Hers is the blade that divides the sea

Sea= Silvertear Lake
Stone= Mothercrystal

Something happened between Midgardsrmr and Hydaelyn involving the Lake which is probably what the sea is referring to (sea is a more poetic word for body of water than a "lake"). Stone is an abrupt diminutive way to refer to a crystal that makes it sound less than remarkable (like calling Earth a "rock"). The blade may refer to Hydaelyn's warriors of light in a metaphorical sense, or maybe literally the blade of light. The spear may refer to the counterpart (so far not shown)