This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
嶹 combines 山 (mountain) with 壽, which likely contributes the sound. The exact historical development is uncertain, and the character is rare.
A mountain 山 beside the complex 壽 shape. Without a clear meaning, picture a mysterious, ancient mountain peak marked by an old, weathered inscription.
For トウ, imagine a tall mountain peak piercing the sky like a tower: tower -> トウ, and the mountain stands alone.