Hey, if you're already reworking promos into boss drops, why not this guy too?
Ancient Sentinel has some really rare and meta-defining drops, which is good and all, but it also doesn't really have anything more common that the majority of players can serve to benefit from. So, Ancient Sentry!
I propose a 6% droprate compared to the weapon frags' 3%, to ensure it's not too hard to get, but you also don't get too many of them, either.
- Now only has 6 ranks (1-3 are removed).
- Now has a deploy limit of 1.
Base HP: 250 > 395
Base Armor: 120 > 180
Laser Blast is unchanged.
Laser Burst now works just like Ancient Sentinel's Nuclear Ray, burning anything it hits for 3 turns. The critical rate is also increased to 10% base, with a 20% chance instead on soldiers and tanks.
Sentry Shielding is offensively unchanged, but the stun chance is raised to 70% on the tile in front of it. This allows it to effectively stun the tiles in front of it, and stall for its' new attack...
Immobilize, the dreaded attack itself. It hits the entire field for 90-131 damage at max rank, with a 30% chance to stun. It cannot crit at all, and its armor piercing is 50%. This attack has an extensive prep time of 5 turns, a long reload of 6 turns, and its' 1 attack range forces the Ancient Sentry to be on the front row for it to be used. In PVP, this means the attack can be stopped by disposing of the Ancient Sentry early in the match, but clever players can place it in the back to 'cook' the attack for when the frontline falls, if the need arises. This all serves to balance the attack in the hands of a player, and more importantly, stop it from becoming absolutely insane in Boss Strike (like Plasma Artillery).
The goal of this design was a strong support unit which specializes in the frontrow, but who can be used as a backup tank and win condition as well if the frontline breaks. Obviously, this isn't a perfect idea, but it'd be cool, I think!

. This would be a cool addition