Not much to tell about this one, really. Sometimes ability to take a punch is more important than dealing the punch. Upon usage this pet will heal your for 240-293 every 3 seconds for 7 seconds - giving total of 3 ticks. At best it is 879 HP resotred in total. Since most assassins are under 8.000 hp this might not be as punny heal for sin as one like to think (more than 10% hp restored).
First of all this heal stacks with both pots and avatar of death so you can combine those to create some pretty nasty healing spike. Back in 1.4 assassins used to have Golden Lotus Extract which was healing about 1-1,5k out of our 4-5k HP pools. Again, this is "free" substitute for that old GLE just like Tree of Death is subsitute for second wind. Obviously this is NOT the pet to use in every fight: you will be much better off using Gray Lotus (more on that gem soon) because of the damage buff. Remember that all the pets are sharing global cooldown of 2m so healing up with Golden Lotus will prevent you from using Gray Lotus.
But when you are in a tight spot and low on HP this just might come in handy. At very least this pet will negate one critical hit from a non-raiding boss like Gray Apes in Paikang, and often that makes enough of a difference ;p
The pet has no radius, just drop it and you will get a buff. Can be used while moving.