The Hero to be Born is a Dot is the first stage in Dot Heroes.
Doge spawns at the start, and continues to be spawned about every 7-13 seconds until 8 have been spawned. Snache spawns ~17 seconds in, and continues to be spawned approximately every 23-33 seconds, forever this time. Those Guys spawn 50 seconds in, and respawn 10 seconds later. No more spawn after that.
When the enemy base is at 90% HP, the boss, Dot Hero, will spawn, along with a Snache. More Snaches spawn every ~23-27 seconds until 8 have been spawned.