Riggu Felis was a wildcat warlord who ruled on Green Isle and lived in a huge wooden fortress. He had a wife, Lady Kaltag, and two sons, Jeefra and Pitru, none of which he was particularly fond of. He was supported by an army of feral cats, who kept the native otters as slaves. His life-long aide was the pine marten Atunra, who cared for him when he was injured and gave him counsel. Riggu was a cruel and merciless individual who would order ruthless slaughter at a whim, but he was also highly intelligent. He was said to be physically very strong.
In battle with the great osprey Pandion Piketalon, Riggu had part of his face torn away by the bird's talons, leaving exposed bone and fangs beneath. After this major injury, Riggu was forced to wear a half-mask made of chainmail, disguising this grotesque wound. Though he managed to stick a star-shaped iron barb into Pandion's mouth before Pandion escaped, Riggu did not forget what the hawk did to him that day, and had his eye on revenge, having his cats butcher any large birds they came across from then on. He was also angry at his sons for failing to kill the bird, and for their constant bickering and spoilt natures. The latter issue eventually caused him to have his sons demoted from their princehood and placed in the barracks to be trained as fighters. He especially worried about Pitru, who showed a disturbing tendency to his father's brutal nature and might wish to rebel.
Riggu encountered trouble several times with Leatho Shellhound, who led his fellows in a rebellion against Riggu Felis. During the skirmishes, Leatho and the otter clans managed to kill some of Felis' cats and free several slaves. Jeefra was also killed, though it was revealed it was Pitru and not the otters who had done so. Felis suspected this was the case, and had Pitru watched by Atunra while Felis pursued the otters. However, she, too, was killed under Pitru's orders. Realizing Pitru was gathering cats to his side as he had feared, Felis had one of Pitru's followers brutally executed as a warning, and Pitru and his followers fled the fortress. Riggu then encountered more trouble in the form of his wife, who was beginning to lose her sanity ever since Jeefra's death, and who blamed both the otters and her husband for it. He had her restrained, and set out to fight the otters once more.
Riggu eventually gained the upper paw in the skirmishes and imprisoned Leatho in a cage. Leatho escaped the cage with the help of Pandion, but his new hiding place was set ablaze when Kaltag escaped her confinement and put a torch to Riggu's wooden fortress. Pandion and Brantalis Skyfurrow were sent to rescue Leatho by Tiria Wildlough.
They carried Leatho down, but Riggu, fighting a battle with the otters below, recognized Pandion and threw his axe at him. Pandion was unable to dodge in time and fell into the lake, dead. Tiria, who had once sworn to pay back the beast who put the iron barb in Pandion's mouth with his own weapon, loaded the iron star onto her sling and fired it straight at Riggu. It hit him dead-center between the eyes. He died with the star embedded in his brain, falling headfirst off the pier into the lake. It was later mentioned that his body was thrown onto the the burning remains of the fortress along with his cat guards.
- Riggu was the only warlord to fulfill his revenge.
- "Felis" is the word for the genus of wildcats.
- On the back of the FireBird Fantasy edition of High Rhulain, the name Riggu Felis has been mispelled as Riggu Felisand.