Cassium Mana Beasts

Cassium Mana beasts are beasts who have either ingested or lived near large deposits of Cassium in a unrefined form. This causes them to sprout large crystals from their body as well behave more abnormally than they would normally do.
  Mana Burned - This beast has been soaked in the magic from unrefined Cassium, this causes the creature to make a Constitution saving throw DC 15 whenever targeted by a spell equal to a quarter their hit die rounded up. On a success the beast absorbs the spell and the damage of their attacks get a +1 die of damage . At the start of the monsters turn it makes another Constitution save against the spell levels it has absorbed so far + 10 (Cantrips count as 1 spell level for this purpose.). If it fails it explodes for 1d4 per spell level absorbed to all creatures within a 10ft. radius. DC 15 Dexterity save and take half damage.
  Crazed - This animal is immune to being charmed and handle animal checks, it attacks indiscriminately.
  Stats - The beasts strength and con go up by one, while its int and wisdom drop by five. Its max hit die increases by 3 and gains resistances to all non magical damage types.