While field bosses were not really engaging, I think the idea of removing them forever seems very shortsighted.
The problem of higher level player farming them in general is that you need those ominous spirit fragments that drop nowhere else to craft drakonas accessories.
For lower level players, they might be a challenge, but that’s not very interesting.
Here is my suggestion how to improve the field boss system:
First of all, change it from a field boss system to a solo instanced type of system, similarly to the Irredian Shelter bosses Madon Maiden and Amist Dog (or however the names are written correctly).
That enables a certain scaling with the level of the player.
I suggest fusing it with the current mercenary outpost missions (e.g.Siaulai,Colosseum), meaning you will be able to open a portal to a location with the field boss waiting for you.
As entry tickets, I suggest using boss monster cards[e.g. Cerberus Card]. This system is easy to utilize, would in general create an initial RNG-factor (as monsters from card albums are random and they only drop a card with a chance of ~50%), but still allow the player to choose which boss monster to fight by utilizing its card.
It also breathes life into the dead card system, where 90% of the cards are completely useless.
If they could be used as entry tickets, every card would have an increased value.
You can also scale the difficulty and rewards by using different star counts of the monster card used for entry (e.g. a 1 star Cerberus card will lead to a fight with an easy Cerberus, but also not very valuable loot, while a 10 star Cerberus card would bring out a very strong boss with very good rewards).
One of the possible rewards for clearing the mission (you will always get a certain type of cube with different rates and materials when clearing the boss fight) could be a card upgrader
which can change the card values (either upgrade or different stats) and possibly turn them into legendary cards.
Other rewards could be ominous spirit pieces, skill boost weapons (that boost the skill levels of a certain class when equipped, e.g. Attila for Priest ), recipes of old weapons that could be used for weapon skins and no longer drop anywhere[e.g. Spearfish Rod], legendary enhancement cards (ripped ones only), black card albums and other items I cannot think of right now.
If you do this, not only do you save the field boss system but also improve the card system and the mercenary mission system in one go.
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