SIMULACRUM PORTALS ACTIVE WHILE ENGAGING BOSS

I FINALLY GOT ALL THE SPLINTERS FOR OPENING THE SIMULACRUM TRIAL AT THE REALMGATE. I'M ABOUT THE 8/15-STEP FIGHTING IN A NARROW SPACE AND A DAMN PORTAL MATERIALIZE OUT OF THE NOWHERE IN THE MIDLE OF A BOSS FIGHT AND APARENTLY I CLICK IT. WHY IS THAT? THE DAMN THING IS NOT IN ANY OF THE OTHER PARTES OF THE TRAIL. WHY IN THE MIDLE OF THE BOSS FIGHT? WHY IN THE MIDDLE OF THAT NARROW SPACE? I USE A DEMONFORM BUILD AND NATURALLY ONCE YOU TRAVEL TO THE PORTALS THE DEMONFLAME STAKS RESETS. SO, I WENT IN AGAIN AND THE BOSS WAS SPAMING EXPLOSIONS AND I LOSE. NOW I HAVE TO GATHER ALL THOSE SPLINTERS AGAIN AND THINGS LIKE THIS MAKE ME WANT TO QUIT.

ANY OTHER WENT THROUGH TO THIS CRAP?