When one of my PC wish to go solo mission with a level 20 rogue with 10 tiers of mythic in Trickster character. Is there any ways I can counter it without have my NPC wearing heavy armor and shield with tons of bonus or giving my NPC some abilities that just makes it impossible to sneak attack?
Are there any simple items or feats, even mythic path ability that can make sneak attack less effective?
Sneak attack is probably the least of you worries with Mythic stuff flying around. Personally, I wouldn't worry about it though, let him have his fun, and if you want to challenge him, throw one of the myriad of "immune to crits and precision damage (i.e sneak attack)" at him.
At this level even classes with certain abilities can become immune to crits and precision damage. Worst comes to worst, give something you don't want to die Heavy Fortification. Then there feats and items that grant you a one-time crit counter (which should also work against sneak attack I believe). I'd be surprised if there wasn't a Mythic equivalent that made you flat out immune. Just don't abuse it though, because that's one of the few things your player has invested in, so let it be useful every now and then.
There are nothing in mythic that makes a character immune to critical hit nor precision damage. Don't want to be mean to just immune the sneak attack, but I don't want him to go solo all the time and double sneak attack on all the important NPC all the time when the rest of my team just trying to stay out of his way.
I know Windy Escape can block one sneak attack, but is there a way to stop the second one just so he learn his lesson and work as a team? Because I just want to teach my team to be a team without focusing them or telling them to. I'm playing the level system backward so eventually they will lose all mythic tiers and levels until level one. So team work and bond is very important for them if they wish to survive.
Thanks.
If he decides to not go rogue, and go for another damage dealing class he would be doing more damage. You might want to think twice before accidentally pushing him onto something more powerful.
No, he means Trickster, the mythic path.
Its capstone is treating opponents as flat-footed constantly, even if they're immune to flat-footed. That makes Sneak Attack pretty much land automatically barring specific immunities.
Jingasa of the Fortunate Soldier can block one sneak attack per day. Light/Medium/Heavy Fortification can negate 25% to 75% of incoming sneak attacks.
Concealment outright negates Sneak Attack unless you take specific measures to counter it, so a simple Minor Cloak of Displacement works fine.
That said, he'll learn to work as a team as soon as he loses that 10th tier. I'd honestly leave him be for now and let him have his fun. You'll yank the rug out from under him soon enough, and having a taste of unlimited sneak attacks will make him much more inclined to do what he has to do to achieve that again.
Thank you! That's very helpful! I do worry a bit if they every get back from level 1 to where they are now, will they become better people, or worse...