#prevention effects

[magicjudge]

If I control a Ria Ovor, Bane of Bladehold and a Gisela, Blade of Goldknight, and I go to combat and target Gisela with Ria Ivor, how many mite tokens will I make when Gisela hits? Since they're both replacement effects do I get to pick the order they apply? Does this change if a third player controls the Gisela and I hit the second player with a different creature targeted by Ria Ivor?

The controller of Gisela is irrelevant here beyond which of her abilities applies to the damage being dealt, so she could be yours or another opponent's and the result would be the same.

So what is the result here? Unfortunately, it's the worst case scenario for you, or at least it's likely to be. Both Gisela's ability and Ria's ability affect the combat damage that the creature would deal to your opponent. When multiple replacement or prevention effects want to modify the same combat damage event, then the player being damaged (or the controller of the creature or planeswalker being damaged) gets to choose which effect gets applied first. In this case, they'll almost certainly choose to prevent the damage with Ria's ability first, leaving nothing for Gisela to double.

[magicjudge]

If my opponent controls a True-Name Nemesis and I control a Soul-Scar Mage, will Anger of the Gods kill their creature? It is my understanding that SSM's replacement effect changes the damage to -1/-1 counters before TNN prevents the damage, but I'm not 100% clear on the timing. Thanks for all your help.

Prevention effects, like from protection, and replacement effects, like from Soul-Scar Mage are handled at the same time. One doesn’t take priority over the other. So, you won’t kill True-Name Nemesis here unless your opponent is feeling generous.

When Anger of the Gods (or any other source you control) would deal noncombat damage to True-Name Nemesis, both the prevention effect of True-Name Nemesis’s protection ability and Soul-Scar Mage’s replacement effect want to modify the damage event. As the controller of the affected permanent (e.g. the permanent that would be dealt damage), your opponent chooses which replacement or prevention effect to apply to the damage event first. If they’re smart, they’ll choose to apply the protection effect first, which prevents the damage. Since there’s no longer any damage being dealt, there’s nothing for Soul-Scar Mage to replace with -1/-1 counters.

[magicjudge]

Hi, I'm a noob on magic and I want to know if you can use "Deflecting Palm" into a Eidolon of the Great Revel... I mean If I need to deal 2 damage to my opponent (for example), can I use Deflecting palm, Eidolon make me 2 dmg, I don't take that and redirect?... And, if I take that 2 dmg, but then I play a Lighning bolt or lava spike or something like that, Eidolon makes me 2 dmg, can i redirect that and deal 5 dmg with the eidolons and the spell?... Thanks a lot :)

Eidolon’s trigger from you casting Deflecting Palm will resolve before Deflecting Palm does, so that damage is going to be dealt to you.

However, you can choose Eidolon as the source when Deflecting Palm resolves, and the damage it would deal to you for casting your next cheap spell this turn will be dealt to your opponent instead, so you can bolt for 5 as you said.

[magicjudge]

If Player A casts Breaking Point, can Player B respond by playing Riot Control and taking the now-prevented 6 damage, or can B not choose to take the damage since it would be prevented?

Player B can choose to take the damage. The fact that it’s prevented doesn’t matter.

[magicjudge]

What happens if I control Gisela, Blade of Goldnight and before I'm attacked cast Channel Harm. Would the damage be halved before Channel Harm prevents it (thus weakening the damage done to my opponent) or would it prevent it before getting halved?

As the affected player, you choose which prevention effect to apply first, so you can just choose to Channel Harm fully. (Don’t forget to have Gisela double the damage it deals to your opponent though!)