Sometime ago I made a suggestion. It was to implement daily achievements such as 'kill X boss with a 1/2/3 star char base attack', or 'beat X boss without having any talismans equipped'. Stuff like that, increasing in difficulty as you complete the challenges. Same would go with the time rift. It would be fun to try and defeat the beast (not on madness of course) with a low star char. You'd have to be careful to not let the enemy kill it and to not kill the beast without the char attack. Something along these lines, maybe with rare souls as rewards.