Good afternoon Eric, it really depends on the type of pet you teach it too... You see the pure ninja monsters( monsters that spawn on tok , with the exception of fire beetles,) once you teach them ninja skill they also gain 100 hideing skill and the ninja UI.. meaning they will shadow strike and use other ninja related moves.... with these pets as their ninja skill increases so does the passive bonus of all ninja moves... the down side to these pets is they often will use moves that makes them hide, vanish and in other ways drop monster agro leaving you with 10-15 mobs and a look on your face like" well I guess I will just die then".. lol as for other monster like the Naj they learn ninja skill passively.. meaning you teach them a move like frez whirl.. and they gain ninja as a skill but not the UI... now there are 2 appealing traits to these types of pets... one is as the ninja skill gains the bonus damage to the ninja related moves will also increase in damage.( always best to take ninja to 120 skill on these pets). the 2nd ones is .. since this school of magic is learned passively it doesn't show up on the UI list and there for does not over write other schools of magic like poisoning on a naj or chiv on a cu/other pet..... Im sure the pure ninja pets have a place for some playstyles.. but as tank pets they fall rather short.. as for the passive ninja pets they are normally power houses and I rather enjoyed testing them... hope this helped mate.. should ya have any other questions feel free to post or message me...=^-^=