haha, so enthusiastic, @dickwad. I think right now @DemonicPolaris94 is just looking for a regular Hound as he starts his Dungeon Quest Adventures. but your advice is good for later when he starts looking for Legend & Eternal Pets for Campaign and Arena.
Hounds: they Fetch any Gold nearby on the ground, and can find any buried Gold. it is possible for them to find and dig up Gold, and leave it behind if you are on another part of the map. I have seen this happen with my own Hounds when I clear a map fast and then go back to get the loot.
Fairy: when your HP gets down to 50%, they cast a Wish/Heal that works just like using a Potion, but it has a 5 second cool down.
Imp: pick up any items you don’t pick up based on your Item Pick Up setting in Options. if you have it set on Rare, the Imp will pick up all Normal and Magic items. for every 5 Normal items, it will drop a Magic item, and for every 5 Magic items, it will drop a Rare item. there is a chance that it will drop better items of a higher Tier than your settings, even Legend or Eternal. if you have the setting on Legend, then 5 Rare for 1 Epic, and 5 Epic for a Legend. for some reason, when converting these items, sometimes there is left over magic that the Imp uses to drop Gold and/or Orbs.
Slimes: +10% Element DMG (Ice, Fire, Poison, Shock, Arcane) and +100 Resist to the same Element. this Boost doesn’t change when you change the Element of the Pet. so if you changed a Poison Slime to Frost, the it will still be Boost Poison, but any affixes that affect Elements would be Ice, like +5,000 Ice DMG.