Cmdr EXP: increase
Infirmary Healing: speed increase
Troop Size: increase
Otto is considered an essential hero as one of his troop skills provides a bonus to Troop Size, which at +5 adds +10,000.
His other troop skills are nothing to sneeze at either, at +5 providing a Cmdr EXP bonus of +30%, and a bonus to Infirmary Healing speed of +20%.
Otto is an economy hero which means he doesn’t need to be evolved higher than level 131.
He can be obtained in Noah’s Tavern.
He can be obtained by Hunting Zombies level 10-14 or Zombie Lairs level 8-9