CHEGG

Food Obstacles: Food obstacles are obstacles that can be destroyed by an attack, but will block attacks from going past them. Pufferfish 's obstacles will cause poison 1 to the attacker if destroyed by a melee attack.
Holes: Holes on the ground are usually caused by an explosion, these cannot be destroyed nor fixed. Creating a hole in a shallow water tile will transform it into a deep water tile, holes cannot be created in deep water tiles.
Cobwebs: Cobwebs are obstacles that will slow down the mob, moving through them will cost you double your mana and will disable your dash. Cave Spider and Spider are immune to it. Cobwebs can only be created in ground tiles.

Official Game Guide

Modifications

Arena modifications that can be applied simultaneously. Multiple can be active at once.

Height

Ceiling

Time

Wall

Obstacles

Weather