Doom is a melee character. His primary attribute is strength. The hero is mainly taken as a hardlaner. Most effective in the mid and late game.
The hero is an extremely useful ally thanks to the Doom ultimate, which weakens the selected enemy and inflicts a dispell curse. Buying Aghanim's Scepter will add Doom AoE effect, which can be very useful in team fights. Thanks to Devour, the character can always find a source of gold consuming a neutral creep and acquiring its special abilities. The Scorched Earth spell is useful both during initiation and retreat. The Infernal Blade ability allows the hero to deal significant damage and is especially effective against heroes whose primary attribute is strength. Aghanim's Shard increases the damage from this ability and makes it even more dangerous in the late game.
He that burns and is not consumed, devours and is never sated, kills and is beyond all judgment. He’s Lucifer. Lashed by inescapable needs, Doom carries his own hell with him wherever he goes. Defiant to the last. Eventually, the world will belong to him.