The energy source Edit
Matter falls into a quasar and gets squeezed so much, that it generates tremendous amounts of energy, far more that it could ever generate by nuclear fusion. As it collides into the central black hole, it also spins very fast (close to the speed of light), creating one of the strongest magnetic fields in the Universe. As a result of this magnetic field, a part of this matter can get removed from the accretion disk (matter spinning fast and waiting to enter the black hole) is thrown away, into two giant beams, traveling close to the speed of light.
A quasar is deadly and unpredictable. Its light changes very fast, depending on what it is swallowing. It also has huge emissions of deadly ultraviolet, X and gamma rays, but because matter is moving so fast inside, photons lose energy traveling outside. So, the highest amount of light seems not to be deadly. Also, quasars generate massive amounts of radio waves. The power they generate (mainly their two polar beams) could be strong enough to seriously affect a galaxy.
Could a planet exist around such a deadly object ?
Possible planet Edit
Quasars generate so much light, that it is possible for a planet to be at 8 light years and be illuminated just like Earth is from its sun. That planet must be not into the accretion disk (it will get squeezed by matter entering the quasar) and must not be in the way of its polar beams. No matter what trajectory we imagine, the planet must pass at some point the equatorial plan, where the accretion disk is. At 8 light years, there should not be many passage points through the disk. A highly advanced technology might be able to open a hole through the accretion disk, to allow the planet to pass. However, plants can survive with a light intensity of 0.1% of what we have on Earth. So, if we add enough greenhouse gasses, our planet could be placed at 250 AU from the quasar. That is a more safer distance.
In theory, a free-floating planet can come that close to a quasar. It can come, but since matter is flowing to the quasar (gasses, dust, planets, stars, everything), the planet will not last long.
A quasar is a giant source of energy. The civilization that will use its potential will rise far above we can imagine today.