Is this on Sim, Private Server, Community server or the MMO?

If it helps at all this is the intent for upgrade controller: https://github.com/screeps/engine/blob/master/src/processor/intents/creeps/upgradeController.js

It has a special case for 'if RCL 8'

if(target.level == 8) {
        var limit = C.CONTROLLER_MAX_UPGRADE_PER_TICK;
        var effect = _.find(target.effects, {power: C.PWR_OPERATE_CONTROLLER});
        if(effect && effect.endTime >= gameTime) {
            limit += C.POWER_INFO[C.PWR_OPERATE_CONTROLLER].effect[effect.level-1];
        }
        if(target._upgraded >= limit) {
            return;
        }
        buildEffect = Math.min(buildEffect, limit - target._upgraded);
    }

Ghodium hydride and its OH/X later boosts can increase how much 'upgrade' you do, without increasing energy cost. So 'maybe' if you had a 14W single creep w/ a boost it could go over the 15 cap? That might be what was meant by the increased limit, as smokeman said, (and noted by effect in the RCL 8 snippet there) power-creeps can increase this limit.

To be clear, returning at this point (in the intent) means you got an OK (intent was generated), but nothing happens (as it returns before changing anything) if your over the limit. This can happen with a few different intents such as a tower executing a repair on an item already being repaired to full by another creep/tower, or a move command into a wall. Their valid intents, but return in the intent causing no change.

Side note: If your looking to get more GCL, and have a GCL free to spare. a "GCL Temple" is a common tactic to gain more GCL more rapidly.

https://wiki.screepspl.us/index.php/GCL_temple

*edited PS: Sorry to hear this has been going on for weeks, would recommend if you haven't trying Screep's Slack, its a bit more dynamic and generally more rapid response than the forums.

I think what was meant was they can 'have' 10 invader cores on expansion at one time, not that they can only spawn 10. I'd agree that if your room is first-chosen by the core it will keep spawning there if you keep killing it.

https://github.com/screeps/backend-local/blob/master/lib/strongholds.js#L238

^ That's the code for the private-server's proxy-invader core spawning if you wanted to take a look.

Have you had this happen recently? O4 said on slack on Dec 24th it should be fixed.

Environmental hazard

• Lava as a terrain type used, causes damage when on the same roomPosition as it, unless a road is used, but road takes a higher decay rate (at the benefit of no damage to the creep)
• Center of map (or highways crossroads) is/are a volcano(s).
• Eruptions occur every x ticks and last y ticks.
• During an active eruption phase, lava terrain tiles generate dropped RESOURCE_LAVA in adj tiles that fills to X amount per tile, then spreads to the next tiles up to Y range if at max amount in-tile. Could generate less in highways/SKs/unclaimed rooms for less objects over all.
• Dropped lava causes high-damage/damage to structures & creeps on the same tile (or adj tile)
• Creeps can pick up Lava, but take damage per-tick that lava is held in their carry. (negate or slow if tough parts used?)
• Dropped lava not next to a lava terrain type, or other dropped lava cools (or placed in a structure to cool/process?) into a diff resource, like RESOURCE_OBSIDIAN or something.
• Could use this new resource as a 'scoring' res like score currently is, turning it in or processing it for points.
• Could also have volcanos on eruption blast 'rocks' out into random rooms which deal damage in an area & take time to land like a nuke, but less dmg/doesn't kill all creeps in a room. Necessitating dynamic moving and/or shielding of structures.

@tigga

(semi-edited / deleted the post I forgot to link to this one)

Holding a controller's 'sign' adding to score over time would prob do, more you have signed, more points your accumulating and could also add multipliers for rooms that are owned/reserved. Would prompt wider sprawl though probably alot of fighting over territory for more score. Everybody could probably easily be on the board, but more advanced could mass-reserve areas to increase score at the cost of energy/spawning.

If it was roomPosition/easy-to-build objects on each roomPosition with your assigned color could add score per-tick per each one, or every x number of pixels (positions) adds a point (like 25 = 1 point per tick). Would also be fairly easy for anyone with creeps around to score just by doing basic movement, more advanced players w/ scouting to score, or way more advanced to path though unowned pixels (positions) in patrolled rooms or finding best route to take to keep an area painted.

Would agree that if it was total count at the end, would be a end-round blitz to paint as fast as possible.

Paint the World

• Each player is assigned a color value.
• Either signing a controller or 'moving onto' a room position 'paints' that room/roomPosition the player's color
• mapVis shows painted rooms/positions
• Player with the most 'pixels' (roomPositions) or rooms painted wins, can score from 'most covered area'.
• Could also 'paint' with energy and have some low eng to build walkable structure as a 'claim' on that room position as well.

Age of Power

• All users start out with some amount of GPL, and may spawn in power-creeps in any configuration desired up to the GPL Limit
• Powerbanks spawn more frequently, or smaller in every room (to allow for more harvesting and/or power creep renewal.
• win condition(s)/'achievements'
  • Longest living power-creep
  • Most power-creeps
  • Highest GPL level
  • Most enemy power-creeps slain
  • Furthest distance traveled from spawn

@gadjung Could do a wonder that's like "The tallest tower" where you pump energy into it like a controller, which builds up its hits 'infinitely', see who builds the one-tallest by end-of-time/season. May be hard to get to the wonder in-time to trash it if not enough people spawned in the area / already were cleared, but I suppose that's part of the challange.