It is very much possible :) the colossus aren't the threat imo, it's the wave just after the first colossus that got me the first time, easy to heal the target of the colossus, he is very slow attacking :D I was very limit on gold through it all :D it's nice,it's the first map where I felt limited with it, I still built a prison and a torture chamber because I wanted to try to convert but the templar aren't very strong at all :< 94min ish to complete =)

And Done ! :D

I usually just place a handful of defences on one side, say the right side...around 5/6 at the bridge area, and constantly watch the minimap. The plan is to amass chunders and skargs. When I see enemy units approaching on either side, I pick up and drop all my units and heal them. I constantly watch the health of whichever unit is being attacked and pick it up and drop it on the beast den to heal it. I try Never to lose any units whilst maintaining the attack.

I am pretty sure that there are only eternals rather than colossi on this map. Eternals have a lot of health but deal very little damage. They can be ignored for a while whilst you take out other units. Use workers and units to split up the enemy army. Place bombards pro-actively to distract units, place blade loti to draw away their attention. Shockwave units to split them up. Do not try attacking the main bases until the main waves are done since, although entirely possible, another wave can spawn and attack meanwhile.

Finally, remember to place lairs before attacking with chunders. Keep building up props/beast den room. You should Never reach the maximum beast den percentage unless it is at maximum size. Build multiple ones to give multiple healing spots. Remember also to always attack with your entire army and to get your rooms built as soon as possible. Aim to have a beast den build before the 30 second mark, and never lose a single skarg unless it is a particularly strong wave (such as the eternal or stone knight ones).

I tried the foundry/defenses route. got minced every time, the death wave with the collossus and all the lvl6 and 8 stuff just trashed them all after ripping the Skargs a new one

Those are workers which are part of the trigger system. Truth be told, it is not worth bothering with gnarlings. Just get chunders. The level is of course possible without editing mutators, and quite simple when played correctly. With that said, the level can also be completed just with skargs.

unlocked barracks before I started and was able to get enough lvl4 gnarlings to repulse the first death wave. went on to complete.
I didn't notice there was a second cultist, possibly if you rush to get both you can get your gnarling force up quickly enough without altering the mutators.
wiped the map clean but there was still a couple of creatures behind walls that never came out to play.

No, it is very possible lol, you must have played it wrong. Try some of the easier maps before the harder ones. These focus on good gameplay and decision making.

impossible - deleted

This level is very much focussed on siege. It is actually just player v. Empire, despite the other three AIs which do nothing generally. The Empire shall try to build underminers, defences, and send waves at the player, so getting a foundry quickly is important, as well as maintaining a strong skarg army. Also be wary of gold, it is important to use it wisely. There is plenty to complete the level though.

Thanks, shall look into it. It seems that one gateway has the wrong setting, and perhaps the eternal comes too quickly.

I played 3 times, the last play, I lasted until about 19 minutes. The deal breaker was the the Eternal. I had all my minions around him, without other enemies, and they didn't really seem to attack until he got near the core. Had him down to two petals, but the core kept getting enemy reinforcements. Never got a single sin, and I think I had 10 skargs before I started losing them. Apparently, I also claimed at least one empire portal, since I noticed I had a couple units come in. I had 2 found cultists, and the crackpot. This last play I tried to keep the workers from getting too far away, but didn't completely succeed.