From Hel to Asgard

Which secrets are kept by this timeless being?
 How much weight their branches have still to endure?
 With a dense foliage it
 Hides a cumbersome truth
 For inwards is a burden of nine worlds!
 Descending from the heavens
 To the top of this giant tree
 The air fizzles and sparks erupts
 From nowhere to see
 Multi colour rainbow named Bifrost
 A highway to mortal's host
 The cosmic tree, never rests, never plea
 It's name Yggdrasil
 Grows of the past and forever will last
 Even with Nidhogg at its hell
 Sturdy roots bind planes together
 From Hel to Asgard
 The spiritual and physical life
 Is carried by elongated arms!
 A channel of vitality to the slums
 As a well, a spring, or a fountain it brings
 Brings the substance outwards
 Defiantly is resists to the passage of time
 To never collapse!
 But it's roots are chewed by the accursed Nidhogg
 Other perils lurks with the form of ants
 With hunger they feast upon it's buds and leaves
 From the underworld
 Serpents attack the most tender wood
 Leaving wide gashes where pieces
 of vibrant bark stood
 Those wounds are repaired
 Every morning by Norns
 Sprinkling them with water
 Preventing its decay
 The cosmic tree, never rests, never plea
 It's name Yggdrasil
 Grows of the past and forever will last
 Even with Nidhogg at it's hell