First Law

   All that lives must die.

The first law, written into the code of the Great Mechanism after the Dawn War is that of the inevitability of death. And beyond that, the connection between growth and death is assured:

   Those that cannot die, cannot live. Life is growth. Without the possibility of death, there is no growth.

This means that those who seek to avoid death and avoid risks grow slower, if at all. Immortal beings such as gods, demons, angels, and elementals hardly grow at all. Choosing to become undead (especially via lichdom or vampirism) stunts your growth. This also explains why adventurers, who risk everything continuously, grow so much faster...if they survive.

Common ways people try to cheat death and their side effects

There are a few ways people try to cheat death. They break down into three big categories--those that seek immortal existence of the soul after death, those that seek immortal existence of the body without dying, and those that merely seek to prolong lifespan beyond the normal amount granted to mortals. None of them are without risk, even leaving aside drawing the attention of the Watcher or his Gleaners.

Immortality after death

1. Ascension. This involves becoming a being with a True Name instead of a Spark. Whether by transformation by elemental powers, adoption into a Diabolical Family, or by being worshiped enough to become an Ascendant in your own right. The result of all of these is that you give up your independence of soul and potential for growth--beings with True Names cannot grow beyond their names of their own accord. Who they are is defined by that Name. And in large part by how and where you get your energy. An Ascendant whose worshipers focus on the martial aspect will find themselves becoming more martially-oriented, for example.
2. Demonification. Taking and trapping a jotnar in your soul. Side effects include not being welcome outside the Abyss anymore unless summoned. And having to eat souls to survive. Growth is limited to what you can derive from what you consume--you are what you eat.

Bodily Immortality

These tend to revolve around undeath or transformations of self.

1. Embedding yourself into an object. This is basically ascension, but of the kami variety. Works...but not forever.
2. Tying your soul to a kami/fey. Also not permanent, and tends to lock you in place. You also take on traits of that being, becoming less and less human.
3. Vampire rebirth. Technically you die. But you're still walking around. Vulnerability to sunlight, wooden stakes, garlic, running water, all the usual downsides. Plus the bloodlust that grows until it swamps your being in a red tide.
4. Lichification. More cerebral and controlled than vampiric transformations, but a dead end. Sure, you can learn. But only what others have written--you'll never discover another fact on your own. Or grow stronger (in terms of spell circles, et al). Plus the feeding necessity so the jotnar doesn't consume you too.

Antigeria treatments

These aren't intended to last forever...on a single charge. Most of them are just fine, unless repeatedly used. All of them suffer from diminishing returns--the more you use any given treatment, the less time it buys you. And all of them result in diminished drive to create and grow.

1. Cloning (via clone, the spell, or other means). It's always you. But never younger than you were when you took the sample. Also, senescence tends to build up as pieces of the soul don't properly transfer. Especially when you died at extreme age. While the processor is younger, the software is old and crufty. One use, fine, especially if it's for emergencies (ie a drive-by stabbing). By about 5 uses you're seeing significant effects. More than that and the clones start aging rapidly.
2. Blood magic (short of outright demonic possession, usually in the form of bathing or imbibing in the vital fluids/anima of other beings). Withers the soul. Sure, your body stays healthy. But you start taking on pieces of the lives/souls/minds of the people who died for you. Requires a strong will to not go insane, usually of the cackling villain route.
3. Alchemical treatments. Herbs and such, properly treated, can keep you appearing young for a long time and even extend your life. Unlike most, this only has the usual diminishing returns issue. Most who use it only slow their aging, not reverse it, which means they end up looking old but acting young, and only for a relatively short time (~20% additional lifespan).