Don't forget that every monster has a set of 4 items to offer (sometimes it is the same item 3 or 4 times) and that there is a percentage of success of morphing an enemy.

For example

Barb-e - 57.1% of missing and gave you one of these : Ribbon, Tonic, Tonic or Tonic. So, this gave you almost 10% of chance of getting a Ribbon. Is it really worth the try?

I'll give you a reference of the other monster Outsider named

Borras - 57.1% of missing and gave you one of these : Ogre Nix, Tonic, Tonic or Tonic
Covert - 57.1% of missing and gave you one of these : Assassin, Striker, Trump or Trump
Didalos - 57.1% of missing and gave you one of these : Cursed Ring, Cursed Ring, Relic Ring or Thornlet
Harpy - 57.1% of missing and gave you one of these : Exp. Egg, Tonic, Tonic or Tonic
Intangir - 57.1% of missing and gave you one of these : Megalixir, Tonic, Tonic or Tonic
Ninja - 57.1% of missing and gave you one of these : Assassin, Striker, Trump or Trump
Samurai - 57.1% of missing and gave you one of these : Genji Glove, Tonic, Tonic or Tonic
Tap Dancer - 57.1% of missing and gave you one of these : Marvel Shoes, Tonic, Tonic or Tonic
Wooly - 57.1% of missing and gave you one of these : Safety Bit, Tonic, Tonic or Tonic

Pan Dora - 57.1% of missing and gave you one of these : Ribbon, Tonic, Tonic or Tonic
Veteran - 57.1% of missing and gave you one of these : Cursed Ring, Cursed Ring, Relic Ring, Thornlet

If you want a set of Imp's stuff, all those monsters give them at a rate of 57,1% of missing : Cactrot, Pug and Pugs

Tintinabar can be morph from one of those 3 beasts along with 3 Tonic at a rate of 57.1% of missing : Spek Tor, Stray Cat and Wild Cat

Magic Urn morphes into a Megalixir or Tonic, just like Intangir

Retainer morphes into a Gengi Glove or Tonic, just like Samurai

Aquila and Harpiai also morph into Exp. Egg or Tonic, just like Harpy