imperishable (adj.)

• amaranthine
• deathless
• everlasting
• frozen
• immortal
• impregnable
• incorruptible
• indelible
• indestructible
• ineradicable
• inexpugnable
• inextinguishable
• invincible
• invulnerable
• quenchless
• undestroyable
• undying
• unfading
• unquenchable