…it could make raids more exciting and fortifying your base would require more thought and effort.
So far if I've gone to the trouble of digging a wide enough moat around a base or building upon a platform of raised ground with suitably steep sides I can essentially just wait out the raids occasionally repairing the walls after the odd projectile impact.
Imagine if some enemies could slowly break down raised terrain e.g. trolls and fuling berserkers could use their logs/clubs to beat down terrain walls, surtling fireballs could crater terrain walls or the surtlings themselves could change in an explode against a wall to create a bigger hole etc.
If that were the case you'd have to actually defend your walls as opposed to just waiting behind/on top of them. A well defended base might then require multiple layers of earthworks and traps, there'd be more reason to build trace italiennes (bastion/star forts)…
…I realise I'm imagining quite a different experience to what is currently provided and it wouldn't be for everyone…
I also realise that I could produce a similar sense of danger and excitement in the current game by not using terrain modification in base defences.
I can see potential issues with this too, e.g. the site of each boss fight could become a crater (potentially filled with water…) with a floating summoning alter or if alters could be destroyed they'd have to regenerate somewhere…
Still, it's fun to think about…
Source: https://www.reddit.com/r/valheim/comments/pnsbhf/imagine_if_some_enemies_could_modify_terrain_and/