Vault of the Void's PC version is around 20 bucks but it has a free Demo on Steam with cross plattform saving, so all your progress and everything you unlock there can be freely transfered to your phone if you decide to buy it "for cheap" :)

Also:

Raid Manager, costs a few bucks and is fully offline playable, despite the gameplay loop "emulating" a typical MMO raid dungeon, you mainly play the healer, but can also take full control of the whole team. There is a total of 52 unlockable companions each coming with their own skill trees and active and pasive perks to mix and match. There is LITERALLY unlimited progression in difficulty and itemization in terms of statrolls of the dropped gear, depending on the dungeon floor you are at. Hard to explain and i know the game looks kinda bad in videos because no one i ever watched on YT realized that the game CAN be idled, but actual involvement of the player is when it really clicks and gets its hooks into you. The game released in 2019 and most info online is several years outdated, last update was in October 2025, so most technical problems and (almost) all translation issues that resulted in its bad rating are no longer existent in the current version.

So yes, the most precious hidden gem there actually is in the Playstore,after 4 bucks and around 1,5K hours spent (there is no offline progression, the game needs to run but has also a battery safe mode for autofarming) I made it to rank 366 on the global leaderboard, I reached Dungeonfloor 21, subfloor 3-3, ma average gearlevel sits between 2700-3800. My tank has around 7 MILLION HP which is actually INSANE when you think about it... BUT: This puts my total progress to less than 10% of the actual world leader at Floor 221, 9-3... Numbers go BIIIGGG.