Unreleased abilities

Rillaboom
Rillaboom's unreleased Grassy Surge ability will complete the set of 4 surge abilities available in SnS. We already have Psychic Surge Indeedee, which has actually been very viable in singles and VGC formats, Misty Surge G-Weezing, which sees very little use as it is completely overshadowed by other amazing abilities, and Electric Surge Pincurchin, probably the least used but most adorable of the surge users.
So how will Rillaboom stack up? It's fair to say that it has the best base stats of surge Pokemon, and Grassy Terrain giving a 1.3x boost to grass attacks coming off a 120 base attack stat will be lethal, paired with nice recovery for a relatively bulky Pokemon. This ability is 100% better than Overgrow and will likely boost Rillaboom's viability making it stronger and also giving it more support options in terms of pairing it with unburden Pokemon, or using it to remove opponent's terrain.
In singles an bulky offensive set with U-Turn would be good for chipping the opponent's team then bringing in an Unburden sweeper to clean up.
In VGC, powerful scarf Wood Hammer's may be more viable, especially when paired with e.g. Dracovish that will appreciate the removal of bulky water types!

Inteleon
On the surface, Sniper, Inteleon's HA, is not looking too helpful. Boosting critical hit damage by 2.25x instead of the usual 1.5x. But if you dive deeper, this ability may actually have some viability. But to understand why, first a little bit about critical hits. Usually 4.5% chance to crit. Can increase chance by 3 stages: 12.5%, 50% and 100%. Increase in chance can be by using moves with an innate higher crit chance or items, abilities or moves that boost crit chance. Using such moves can actually be useful for pokemon with the Sniper ability with such a huge damage boost and allowing you to ignore opponent's defense boosts.
So how does this help Inteleon?
It only has access to one high crit chance move, but it's a good one - Snipe Shot, it's signature move, has an increased crit chance (though this is not mentioned in the in-game move description!). It also has access to Focus Energy to boost crit chance by 2 stages (though it is slightly frail so setting up might be tricky). Or alternatively it can hold the scope lens for a 1 stage boost.
How could this translate into practice? Focus Energy + Life Orb + Snipe Shot is actually insanely powerful, after one F.E. you always crit with Snip Shot and so can afford to run LO instead of Scope Lens. Can OHKO bulky pokemon like Hatterene and Togekiss just as examples. If setting up a F.E. sounds too risky, you could even try pairing it with Gigantamax Machamp. G-Max Chi Strike also gives a F.E. boost, so Protect turn 1 and Chi Strike, then crit Snipe Shots all day.
Final thing to think about is Inteleon's own G-Max form coming in DLC (the long-awaited Pokemon Gun!). Can only hope that its G-Max move always crits or boosts crit chance like Chi Strike cos that would be awesome!

Arctozolt


Dracovish