Trial of Ascension needed like Summoners Wars has.
Like SWGOH, Summoners War has been around to play for over 10 years, 12+ to be precise. Both games are collecting characters, leveling them up, battling them in PVP & PVE, mods ( runes ) and leveling them up as well.
A few differences are in SWGOH you have only one of each character, Summoners Wars ( SW ) multiple can exist as well as using duplicates to upgrade skills.
One mode that SWGOH could emulate from SW is a trial of Ascension. It consists of 100 levels for easy and hard modes and 10 levels for hell mode. Rewards consist of scrolls to summon 3 star monsters ( 5 star monsters being the rarest ) Crystal rewards every level ending in 5 ( I.e. 5,15,25,35…) increased at each reward level.
Energy for Trial of Ascension ( TOA ) is normal energy, but as SWGOH is stingy with energy, a new energy may be needed. SW currently has 500 energy max and so much bonus energy given I am always maxed out daily.
TOA type game would work and bring in more play time to SWGOH and would probably be better than Colosseum. Imagine 200 plus levels to defeat over a month? Finding the right team comps, and earning more rewards.
SW is still earning money for Com2Us and is a great game with so much content and a great tutorial system.