Even though Underlord is associated with (green) fire, he appears to be interested in ice enough to be enthusiastic about the prospect of a storm of fire and ice when ice-based heroes are on his team. It may seem strange at first, but consider this. Underlord's origin is described to be so deep Beneath the Earth that there is magma above his home, suggesting that for Underlord and his underlings, they've never even known the existence of ice, having only ever been in contact with heat, fire and magma until recently when they went up to the surface to conquer the world, which is only helped further by his claim to Winter Wyvern that "There is no winter in the Abyss". In other words, while it may be mundane to us, ice is downright exotic and alien to the Abyssals, thus explaining why Underlord is interested in it! It's also possible that they're particularly vulnerable to ice, only enhancing Underlord's interest in it as a potential weapon to conquer the surface with.
In the special presentation leading up to the Monkey King reveal, false smoke was filling the lower parts of the arena. In the 6.79 patch for All-Stars, one of the main components in summoning Monkey King was Riki's Smoke Screen.
Sven's God's Strength makes him superhumanly strong for a duration. As Sven is half-Meranth, a species that lives underwater and thus can be assumed to be naturally stronger than land dwellers, God's Strength is likely Sven tapping into his Meranth blood to achieve greater strength.
Why do Legion Commander hate bears? Because Ursa, the resident bear hero (not counting Lone Druid in his bear form) has Fury Swipes, a passive ability that racks up base damage on enemies he attacks. Her Duel do not cancel Fury Swipes.
The Tip of the Spear comic leaves it unstated, but it's easy to reason out why "Moerbeek's finally ready to fight." - the city ran out of food but did not want to surrender and so their forces sallied out to try to fight off the Bronze Legion, hence why Marcus mentioned there was no food found in the city.
