A caster who performs a conjure earth elemental spell summons an earth elemental to do his bidding. The elemental is 60% likely to have 12 Hit Dice, 35% likely to have 16 Hit Dice, and 5% likely have 21 to 24 Hit Dice (20 + 1d4). Further, the caster needs but to command it, and it does as desired. The elemental regards the caster as a friend to be obeyed. The elemental remains until destroyed, dispelled, sent away by dismissal or a holy word spell (see the conjure fire elemental spell), or the spell duration expires.
Notes: Common for druids (PHB).