'Hardest' achievements

[Allexium]

Hello there! So I'm hunting for KR: Origins achievements at the moment. I'm currently missing 14. So some of them I can get by myself, but with others, I think, I need some help. These include:
Valar Morghulis
(Mark a total of 5 targets simultaneously.)
Beornings
(Have 8 or more Runed Bears in any single stage.)
Killtacular!
(Crimson Sentence 10 enemies in a single wave.)
No Pain, No Gain
(Deal over 100 000 damage with Sylvan Curses.)
Wildfire Harvest
(Throw 1 000 Burning Nuts.)
So yeah, I have problem with getting these achievements. Anyone have a tips on how to get them (quite) easily?

[Allexium]

UPD: Just earned Valar Morghulis. 14 Wave of The Ascent was the key. Maxed out Hunter's Mark on some of Golden Longbows, then I got the achievement when 5 Boars were marked. P.S. Make sure you don't have final star upgrade for Archers - it's allows them to kill enemies unusually quickly and thus ruins Hunter's Mark (while it very helpful at normal gameplay)
P.P.S. Boars tend to be good targets for this achievement - they have high health and armor, thus, won't be killed by archers that quickly, plus they tend to come in packs big enough so you'll be able to earn Valar Morghulis on them.

[Allexium]

UPD: Killtacular! done. Achieved at Duskwood Outpost. Started building Golden Longbows at wave 13 with Crimson Sentence level 2. Earned at the last wave with 5 Bows. Seems that the achievement is luck-based.

[Barrows]

The rest of locked achievements from your list I got on Neverwonder map. You can earn gold there by playing the Shroom Game with a gnome. No pain, just lots of coins and towers with upgrades.

[Allexium]

Originally posted by Barrows:

The rest of locked achievements from your list I got on Neverwonder map. You can earn gold there by playing the Shroom Game with a gnome. No pain, just lots of coins and towers with upgrades.

Neverwonder... I forgot that there's a Shroom Money game. Much thanks! I'll take that into account.

[Allexium]

Got Beornings on Tainted Pit, along with The Banner Saga. Didn't knew that this stage would generate such a money. Also found it great opportunity for No Pain, No Gain.

[Allexium]

Achieved No Pain, No Gain on Tainted Pit. As I've mentoned, this stage is great for this achievement - lots of Shadowspawns for damage and nice choke point for Arch-Druids.