Dome of Spikes

you summon a dome of vines with spikes to surround you and allies the plants protect from spells except fire and necrotic damage and if the enemy hits the dome with melee weapons the vines damage the opponent with 2d6 piercing damage. at higher levels the damage caused by the spikes increase from 2d6 to 4d8 damage. the dome has 100 health but takes extra from fire and necrotic