Keywords: Mono black control, recursive etb abuse. Life is just a tool.
Why chainer?
He's probably the most versatile reanimation general, being able to dig up creatures in your graveyard but also in opponent's graveyards. He does come with some challenges, like being suicidal and mana intensive. As a consequence, you need to adapt your deck building to get the most out of him. The need to build around him is something I enjoy, because it automatically leads to a deck with strong themes.
Chainer is also one of the only mono black generals able to blast artifacts and enchantments relatively easily... just abuse the graveyard of your green-white opponent!
Unfair stuff (aka win conditions)
The deck contains a few synergies or combos that can enable a win. I rarely win using creature beatdown.
Chainer + sac outlet + kokusho/gray merchant of asphodel:
The signature move of many chainer decks. Bleed your opponents to death. Requires a ton of mana, but that is precisely one of the strengths of mono black.
Contamination + bitterblossom/ophiomancer:
Lock decks out of mana
Phyrexian altar + grave titan + blood artist + chainer:
Infinite loop that will bleed all your opponents. Being 4 cards, it's quite difficult to get going
Necropotence + Venser's journal:
Not a win con, but if your opponents are foolish enough to leave these two cards on the battlefield, they will loose to your card advantage.
Xiahou Dun + Living Death:
ETB trigger festival... Every turn!
Favourite card in the deck
Tortured existence. Fantastic graveyard enabler at instant speed. You can really use it to surprise your opponents. End of turn dumping in graveyard + surprise reanimation through Chainer is fun!You can also use it to avoid paying commander tax by letting Chainer go to the graveyard.
Other graveyard decks
Your reanimation with Chainer is instant speed, which you can use to disrupt their plans. Cool trick: use chainer's exile clause to permanently get rid of their creatures. This is the reason why my deck does not include graveyard hosers. If you face a lot of graveyard based decks, especially mass reanimation decks, you will have to use more graveyard hate than I do.
Match-ups
This is based on my limited knowledge within my multiplayer playgroup, do not take this as a general rule.
Decks that win through the red zone
Most creature decks will have a hard time to deal with the high number of creature killers in your deck. Be careful not to kill yourself by draining too much of your life when facing a lot of aggressive decks. Sigarda is not a nice girl, but board wipes can take care of her. Creature decks is the match-up for which this deck was built with a fair chance of winning the game.
Combo decks
Guess what? You have nothing to stop them. If you play a lot against combo, your best bet is to include more discard/extract effects in the deck. Chainer can perfectly be built as a discard master. But still, winning won't be easy, because you will lack the ability to control the stack.
Traditional control decks
Prepare for a grindy match-up. Counterspells are not really an issue as long as they send stuff to the graveyard. Same goes for board wipes. If you can outdraw your opponents, you will have a good chance of winning. Key here is to play chainer when you can get the most out of him, so that he can generate card advantage before he gets removed (which will certainly happen when facing a good control deck).
Decks packing dedicated grave hate on enchantments will be difficult to beat (RIP is a huge problem), because they stop your card advantage through recursion. Torpor orb is also an issue, but luckily it will not stop a Kokusho chain.
Stax
I never played against a dedicated stax deck. Given the amount of mana this deck requires. I anticipate a difficult game as stax will certainly attack your mana.
Biggest omission
Exsanguinate and artifact mana doublers. I played with these cards for a long while but refocused the deck on creatures. The mana doublers + exsanguinate strategy is so effective that I found myself tutoring for it quite often. This lead to repeatable games. I enjoy the deck more now that it is more creature centered, but wouldn't blame anyone for playing the highly effective exsanguinate strategy. If you are a real fan of it, you might want to play Maga, traitor to mortals as your general.
A little conclusion
Get the swamps into play and have fun! Comments are always welcome.