Armello

For this achievement you need to beat another hero with +8 Overkill [Edit: originally thought it was 10]. For each spell card you play as Brun, you get an additional fight dice.

This achievement is definitely a multiple turn set up. Your first goal is to increase your Wits and Spirit, and gain as much Rot as you can. Plan on hitting another hero (NOT Sana) when they have some rot, and turn off Quick AI turns if you have that option on.

[EDIT: Courtesy of Kumekerion --
You can make this a bit easier on your self by selecting the AI heroes you play against. I used it to pick low fight/low body heroes with the worst ring for them and the rot amulet. I can confirm that you still earn achievements when selecting the AI heroes and now they should be easy prey with a bit of rot to help you out when you become corrupted.]

Your goal is to take down the health of your target hero after their turn but before you draw cards. Ideally, this would happen right before the night cycle (to get more Magic) but I was able to accomplish the achievement during the transition to the day cycle.

The three cards that are going to help you the most are:
-Aflame (-2 health; Sun’s explode until end of target’s next turn)
-Mirror Image (In Battle, Enemies have -2 Fight until the end of your next turn).
If you get these, store them away. They are crucial.
“Wild Born” (+ 5 Magic next time you enter a stone circle) - this is very beneficial to play at any time early in the game and then AVOID Stone Circles until you need the +5 Magic bonus.

Start the game by finding gear to equip, preferencing anything that gives you extra dice, swords, or piercing attacks. Skip anything that does defense. Once you have at least two gear equipped, start stocking up on Spell cards.

If you see any of these cards, save them for strategic use:
-Aflame (-2 health; Sun’s explode until end of target’s next turn)
-Evil Eye (+2 Wits until end of next turn)
-Feral (+2 Fight, -1 Wits)
-Focus (+2 spirit)
-Glamour (Steal 1 card)
-Immolation (damage health by distance)
-Lightning Strike (-3 health)
-Wake the Trees (Target Loses 2 Cards from their hand)
-Wyld Born (+5 Magic the next time you enter a Stone Circle)

These low cost cards should be saved to pump Brun's hero power:
-Bark Skin (+2 Body, 2 Magic cost)
-Call of the Worm (+1 Rot cost)
-Cursed Lands (1 Magic cost)
-Divination (1 Magic cost)
-Malice Rising (+1 Rot cost)
-Moonbite (1 Magic cost)
-Plague (+1 Rot cost)
-Shimmer Shield (1 Magic cost) *Do not play on your target
-Tanglevine (2 Magic Cost)
-Wyld’s Warning (1 Magic Cost)

Once you have a good stock of Spell cards, you will want to:
1. Plan to increase your available magic
2. Get your target’s health low
3. Play any “Until End of Next Turn” cards before your draw phase with the exception of “Feral” which you would play after your draw phase.
4. Play “Aflame” and “Mirror Image” to give yourself more dice and take away theirs.
5. Attack and use cards with Explosive effects ONLY.

Once you have gear equipped, several low cost spell cards, and more rot than your target (for me it was Thane), do these actions after your target’s turn, but before your draw phase. Also, play Wyld Born well before the “attack” plan and do NOT go into any Stone Circles to trigger the +5 Magic
1. Get in range of Targeted Hero and Stone Circle
2. Have at least 5 Magic and 2 or 3 health.
3. Damage Target with Immolation to get the hero to 1-3 health from 5. (2 Magic)
4. Play “Evil Eye” (3 Magic)
5. Play “Focus” ONLY if currently in day phase(3 Magic)
***At this point, if you have MORE Magic available, play any other “Until End of Next Turn” cards on yourself except for “Feral”.
6. Let the day/night phase change in order to draw cards again.
7. Pick all spell cards.
8. Move into Stone Circle to trigger the “Wyld Born” bonus, with enough movement to get to your target.
***If it’s changing to night, you should have enough Magic already, but the extra health and magic is great.
9. Play “Aflame” on yourself if you have not already. Watch your health as you will lose 2 health in this process.
10. Play “Mirror Image” on yourself if you have not already.
11. Play “Feral” if you have it and have not played it yet.
12. Play as many low cost spell cards as possible.
13. Attack your target. If you don’t get Annihilation, quit and try again, playing different low-cost spell cards to change the seed.

Ideally, if you have the Rot bonus, you will have extra dice, plus one extra fight for each spell you played. With the addition of Mirror Image, your target will have less dice as well. This will see you having a great deal of dice to hopefully explode through the “Aflame” spell, natural explosions, and you’ll have enough to get the +8 overkill for Annihilation.