The Apocalypse attack is an anti-Caro-Kann weapon.
The main point of the Caro-Kann is to achieve a better French defense, possibly at the cost of some tempo. By better French defense, I mean a solid defense where Black holds a pawn on d5 but hasn't trapped their light square Bishop and will typically develop it to f5 or g4 before pushing e6. By loss of tempo, I mean that in a lot of lines when White does not initiate the pawn trade on d5, Black will play pawn c6 to c5 to trade it for a central pawn. For example :
[Title "Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense AKA the better French"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 c6 2. d4 d5 3. e5 c5 4. c3?! (4. dxc5!) {White should realize this is not a French and initiate the exchange while they still can, forcing e6} Nc6 5. Nf3 cxd4 {else White can take and try to hold onto the extra pawn} 6. cxd4 Bg4 7. Be2 e6
One flawed idea in the Apocalypse attack for White is to gain the Bishop pair with 5.Bb5?! almost no matter what Black played, for example :
[Title "What White should probably not do"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nc6 5.Bb5?! Bd7 6. Nxd7 Qxd7
If anything, Black can dodge that trade by playing Nd7, but they really aren't bothered by it at all, they are willing to trade their Light square Bishop for White's King's Knight in the first place, White is really doing them a service spending their own moves making it happening.
Instead, the correct main idea of the apocalypse attack, is that Black cannot move their light square Bishop out of the pawn chain for a long time or at all, and might end up being forced to play a position that looks more like a French. Whenever Black plays Bf5, White instinct should be to look at Qf3, threatening f5, f7, d5, and sometimes even b7.
For example :
[Title "The apocalypse"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Bf5?? (4... a6 5.d4 Bf5? 6.Qf3! e6 (6... Bg6 7.Qb3) 7.Bd3) {more accurate than starting with Bb5+} 5.Qf3 e6? {not the best move, but other ones are still losing} 6. Bb5+ {White is winning}
When Black does fall for one of these traps as players new to the Caro-Kann often do, all hell breaks loose, hence the name of the opening.
But even knowing not to fall into these traps it is still difficult for Black to develop a plan.
If they capture the e5 knight prematurely, they get the worse of both the French and the Caro-Kann, with a very annoying pawn on e5 but no Knight able to target it, and still no good way to get their Queen's Bishop out. For example :
[Title "The worse of both world for Black"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nd7 5. f4 {d4 is also playable and the stereotypical move, but if Black is to take on e5, recapturing with the f pawn and then playing d4 is even better. Black shouldn't capture on e5, but by playing Nd7, they either intend to or are giving White enough time to play both f4 and d4} Nxe5 6.fxe5 e6 {Black still has to worry about Qf3, and cannot play Bf5} 7.d4 {now Black has no good square for their King side pieces either and have to worry about moves like Qg4 and Bd3}
Finally, if they first develop both their knights, as they probably should, playing Bf5 is still risky if White went Nc3 as White can now throw g4 and g5. For example :
[Title "more spooky stuff"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nf6 5. d4 Nc6 6. Nc3!? Bf5 7.g4 {and Black's Bishop has no option but to go home on d7, and Black has to worry about g5}
