Berserk Tetsucabra

Amphibious. The tetsucabra can breathe air and water.

Reckless. At the start of its turn, the tetsucabra can gain
advantage on all melee weapon attack rolls during that
turn, but attack rolls against it have advantage until the
start of its next turn.

Standing Leap. The tetsucabra's long jump is up to 20
feet and its high jump is up to 10 feet, without a
running start. In addition, the tetsucabra does not incur
attacks of opportunity while moving with a jump.

Multiattack. The tetsucabra makes two Gore attacks and
one Stomp attack; Or it makes two Boulder attacks.

Gore. Melee Weapon Attack: +7, reach 5 ft., one
target. Hit: 13 (2d8 + 4) piercing damage.

Stomp. Melee Weapon Attack: +7, reach 5 ft.,
one target. Hit: 15 (2d10 + 4) bludgeoning damage.

Rock Throw. Ranged Weapon Attack: +7, range
60/240 ft., one target. Hit: 13 (2d8 + 4) bludgeoning
damage plus 7 (2d6) fire damage.

Deadly Leap. If the tetsucabra jumps at least 15 feet as
part of its movement, it can then use this action to
land on its feet in a space that contains one or more
other creatures. Each of those creatures must succeed
on a DC 15 Strength or Dexterity saving throw (target's
choice) or be knocked prone and take 20 (3d10 + 4)
bludgeoning damage On a successful save, the
creature takes only half the damage, isn't knocked
prone, and is pushed 5 feet out of the tetsucabra's
space into an unoccupied space of the creature's
choice. If no unoccupied space is within range, the
creature instead falls prone in the tetsucabra's space.

Explosive Rock (Recharge 5 - 6) The tetsucabra digs up a
giant explosive rock that fits in a 10-foot-cubed area.
The rock then rolls into a space, the tetsucabra can see,
within 20 feet of it.
On initiative 20, the rock explodes and each
creature in a 30-foot radius around it must make a DC
15 Dexterity saving throw or take 42 (12d6) fire
damage on a failed save, or half as much damage on a
successful one.