In Dota2, there are several different kinds of heroes. Carry, mage, support, and tank are the main 4 that you'll see along with the other subclasses like pusher, ganker, and jungler which are stacked onto the other 4 main types.
Carries are almost always Attack Damage (AD) based, which means that they rely more on beating the lights out of someone to kill them. Heroes like Sven, Phantom Lancer, and Luna all rely on building items that will increase their primary attribute and overall damage, like a Butterfly, increases damage and agility, or an Abyssal Blade, increases damage. Carries usually have very poor starting damage and require gold to build items to make them effective in the late game.
Mages are heroes that rely on their use of abilities to kill other heroes. They will mainly build intelligence items to give them increased mana so they can use more abilities but there are a few exceptions. Tiny, for example, does a lot of auto-attack damage but with each level of his ultimate ability, he loses attack speed greatly and therefore is not effective and killing people quickly. But his abilities stack on top of eachother and cause amplify the damage of eachother, making him a very tanky mage in a sense. Mages are also usually ranged and have decent starting attack damage but never really get any more because their item build is so focused on the increase in intelligence and although the increase of your main stat increases damage, it is usually very little.
Supports are a very important role of the game as well. While usually lacking in damage and ability strength, they will utilize stuns and other forms of disables to neutralize the other team so that your team can do a lot of damage with taking minmal damage to your own. Some of the most utilized the supports in the game are Earthshaker, Shadow Shaman, and Enigma. What all three of these heroes have in common is that they have very good crowd control. Earthshaker can stun multiple people and block pathways while Shadow Shaman is can neutralize the enemy carry with 2 disables he has. Supports also have completely different kinds of item builds, usually focusing on building items that give utility such as the Mekanism's heal and the Scythe of Vyse's 3.5 second disable.
Tank is usually a fighter that gets a lot of health. Tiny can definitely be considered a tank since his passive grants him large amounts of armor and a passive mini-stun that can activate when an enemy attacks him. Tanks will usually try to initiate on enemies and get them to attack him while the support neutralizes them and the carries and mages do the damage.
For this project, I decided to go with the class that I enjoy the most. The Support Caster. I've decided that there aren't enough demon-like creatures in Dota2 (I think Shadow Fiend is the coolest looking hero). But this is going to be a demon with some quirks about him.
He's goin to be an imp-like creature weilding fire abilites and a strong disable as well as a passive. He's going to be short and have a high pitched, squeaky voice and he's definitely going to laugh a lot and you can bet it's going to be maniacal.
For his first ability, I've decided to be a combination of Jakiro's Macropyre and Ice Path. Sticky Lava is going be a cone shaped aoe abiltiy that he spews from his mouth in a 400 range AoE. If enemies are caught in the effect, their movement will be slowed by 20% at level 1 and take 30 damage per second. Scaling per level will be as so:
Damage Type: Magical Range: 400; Cone AoE
Level 1: 20% slow 30 damage/sec
Level 2: 30% slow 60 damage/sec
Level 3: 40% slow 90 damage/sec
Level 4: 50% slow 120 damage/sec
His second ability will be his passive, Fire Storm. While near enemies the air around him will super heat and do magic composite damage to those around him. This damage is amplified the more enemies that are around him. It does 10 damage per enemy that is around him at level 1 and scales as so:
Damage Type: Composite Range: 150 AoE
Level 1: 10 damage/sec/enemy
Level 2: 15 damage/sec/enemy
Level 3: 25 damage/sec/enemy
Level 4: 30 damage/sec/enemy
These are the 2 abilities that I've put the most thought into although for his ultimate, I have been thinking that it needs to relate to the gates of hell somehow, dealing a lot of damage in an AoE.