Fernian Lancer

A heavy, half-meter sized dodecahedron of polished brass, warm to the touch and covered in access panels. Inside, powerfully charged Khyber shards hum with elemental energy, linked to coils of metal and engraved magic ready to be unleashed.
As an action, a creature can touch the Lancer and expend a 3rd level or higher spell slot, priming the weapon. At this point, its activation sequence begins.

Rounds	Effect
0	The Lancer grows red-hot. Any creature or object touching it suffers 2d10 fire damage, and a creature must make a DC 17 Constitution saving throw or immediately drop the device.
1	The heat builds further. The damage for touching it increases to 4d10, and a creature must succeed on a DC 17 Constitution saving throw or immediately drop the device. All creatures and objects within 30 ft. must succeed on a DC 17 Constitution saving throw or take 2d10 fire damage, and unattended objects are ignited.
2	Dozens of enormous metal spears uncoil and shoot out. All creatures within 120 ft. of the lancer must make a DC 17 Dexterity saving throw or become impaled, suffering 6d6 piercing damage.  Structures in the area are struck automatically, and any given Large or smaller object is struck on a d20 roll of 11 or higher. The lances have 30 hit points, and are immune to all conditions, poison and psychic damage. An impaled creature can be freed by it or an adjacent creature spending an action to attempt a DC 17 Strength (Atheltics) or Dexterity (Acrobatics) check.
3 - 5	The heat builds further, pulsing out through the lances. Each round, every creature impaled by a lance suffers 4d10 fire damage, with structures suffering double damage. All creatures within 30 ft. of the device must succeed on a DC 17 Constitution saving throw or take 2d10 fire damage, both damage rolls increasing by a further 1d10 each round.
6	The device releases all of its built-up heat, exploding and filling a 150 ft. radius with intense fire. All creatures and objects in the area must succeed on a DC 19 Dexterity saving throw or take 10d10 fire damage and be knocked prone. All creatures impaled by lances that are reduced to 0 hit points by this damage are burned to ash; structures are burned out beyond recovery. The area remains on fire until extinguished, and becomes difficult terrain, dealing 1d10 fire damage to any creature that ends its turn there.

Item type

Weapon, Explosive