Not all bosses, only one or two. I beat the rest of bosses alone! BUT, I had all the knowledge of Demon's Souls.
Humanity is a VERY rare asset, so don't waste it! Humanity can make you alive again, and when being alive, consuming humanity adds bonus to your skills, but I don't advise you to do this. You need to be alive and reach the gargoyles. If you do, BEFORE entering the mist to fight them, you will usually fin different kind of signs in the floor. It's the people you can conjure. In very specific fights, you can recruit an NPC to fight with you, like this Knight you talk about. But that's rare.
And it's just better to cnonjure other people. I played it months ago so I don't know how crowded the servers are right now, but when I played, there were signs to conjure people before each difficult boss, so you can call 1 or 2 players to help you.
If you do, please take into account the following:
- The people you can conjure are in hollow state (aka dead). When you are dead you can be summoned, when you are alive you can summon. That's how it works.
- If the summoner (in this case, you) dies, they all die and summoned spirits are sent back to their worlds without reward. That's why you have to be cautious and don't expose yourself when you are the summoner. Usually, veteran players will protect you. It's better that you let them do the main work and try to attack the Gargoyles from behind, etc... Try NOT to be the Gargoyle target.
Gargoyles are weak in their tails. Take profit of the Gargoyles being attracted by the other players!
- The summoned players CAN'T use Estus frasks, so they CAN'T recover health during battle. BUT, if you use Estus or recover spells near them, you can fix them! Another reason why it's better to let them do the dirty work first while you watch over them.
- It's probable that one or all of the summoned spirits die before ending the boss. Then it's the time for you to take a bit more risks and try to finish the battle.
- If you defeat the Boss, all the summoned spirits earn humanity, get alive and receive other interesting rewards. You can also rate them.
- If you die, you have to use humanity to get alive again and summon people. That's why I advise you to don't waste humanity at all. Keep it to be able to do co-op on very specific bosses. Gargoyles are amongst the toughest bosses of the game for newbies. But there are tougher bosses ahead. Keep some humanity to be able to do some coops until you beat the boss.
- Don't forget to salute the summoned players. As there's no chat the only way to communicate is doing gestures. Press SELECT and select a kind gesture to salute the people who are ready to die for you!
Usually you won't find trolls in this game. Because of the very nature of the game and the multiplayer, people tend to be very helpful and kind.
It's a very twisted mechanic, but it makes the game very original and the multiplayer is quality.