Base Stats
Strength: 22 + 3.3/level
Agility: 15 + 1.1/level
Intelligence: 18 + 1.6/level
Armor: 1
Attack Cooldown: 1950
Base Attack Damage: 44-52
Range: 300
Projectile Speed: 1000
Movespeed: 280
Level 1
Strength: 22
Agility: 15
Intelligence: 18
HP: 568
MP: 234
Armor: 3.10
Damage: 66-74
Attack Rate: 0.59 attacks/sec
Level 25
Strength: 121
Agility: 61
Intelligence: 76
HP: 2449
MP: 988
Armor: 9.54
Damage: 165-173
Attack Rate: 0.83 attacks/sec
Skills
Incendiary Round

(not representative of HoN tech level)
The Siege Tank fires an Incendiary Round which explodes on impact, dealing normal damage and setting the ground alight in a 175 radius for 10 seconds. All enemy units take 11/19/27/35 Magic damage/second while standing in the fire.
Attack Modifier
30 Mana
5/4/3/2 second cooldown
Notes: Provides some minor teamfight utility as well as good pushing. Small AoE requires a disable to take full advantage of the damage vs. heroes and other player controlled units.
Fragmentation Round
(actually half of a fragmentation round)
The Siege Tank lobs a fragmentation round high into the air, dealing 40/60/80/100 Physical Splash damage in a 250/300/350/400 radius upon impact.
0 Mana
7/6/5/4 second cooldown
Target Position
Cast Range 800
Projectile Speed 250
Notes: A slow projectile allows this ability to be dodged. Useful for lane presence and farming. The relatively poor damage is accounted for in the mana cost (free).
Deploy Stabilizers
(unfortunately the Siege Tank does not come equipped with a backhoe)
The Siege Tank deploys its stabilizers, becoming Immobilized but increasing its attack range to 750/800/850/900 until they are retracted.
Toggle
75 Mana
5.5/5/4.5/4 second cooldown
Self
5.5/5/4.5/4 second channeling time
Notes: The long channeling time makes this ability very dangerous. The Siege Tank can be stunned during deployment, preventing it from gaining attack range on a tower/building. It may also be prevented from moving with a well-timed stun when retracting the stabilizers. Portal Key will not work, preventing easy escapes while deployed. Tablet of Command and teleports will still work.
Siege Mode (Ultimate)

(this painting of a siege is not representative of the ability)
The Siege Tank engages Siege Mode, gaining 100% Strength and the Siege combat type while suffering a 50%/40%/30% movement slow. Now it's time to find some buildings.
State is StatusBuff so it may be purged by enemies.
150/200/250 Mana
60/50/40 second cooldown
Self
15 second duration
Notes: Siege type deals 0.5x damage to heroes, so this ability is less useful for hero-to-hero combat. The Siege Tank can absorb a great deal more damage, but with a slow movement speed it is also far more likely to. Damage against buildings and other non-hero units is drastically increased. Escape is very unlikely. Best used in combination with Deploy Stabilizers when movement is already impossible.
Etcetera
Inspired by Starcraft's Siege Tank and DotA's Sidereal Engine.
This hero can and will melt buildings, but it offers limited usefulness in ganking and large battles. In the best case, this hero can provide a significant monetary advantage early in the game. Late in the game, poorly scaling abilities and attack damage will put in alongside Nymphora and Glacius in usefulness, although with less utility and more durability.
Mobility items (Assassin's Shroud, Portal Key, etc.) will assist in getting into position to bombard buildings. Shrunken Head will possibly be useful in preventing the Siege Tank from being turned into a sitting duck. Otherwise, support items seem the most likely purchases.
Engineer should never be allowed on the Siege Tank's team if you don't like giving the other team free gold.