These do feel like Invasion era cards. There have been numerous wording and templating changes to how rules text is written, but I get the intention of the cards.
Mostly the issues tend towards things I described above. Take Helcaraxe, for instance. Every turn I can block, sac the enchantment to regenerate the creature and then replay the enchantment to do it again, which bogs combat down to nothing happening. And the most typical way for many colors to deal with Auras - killing the creature in response to the aura being cast, doesn't keep the aura from recurring.
It is odd having so many named characters without marking them as Legendary. I'm assuming that was an oversight.
Lothlorien needs to specify non-land permanents. If your opponent doesn't have an early play and you can hit them with this to put a land back in their hand, you are creating the most unfun play pattern in magic. This is why land destruction is now very limited and surgical about hitting land utility without disrupting the ability to cast spells.
Osgiliath doesn't work. Giving a land Flash does not actually let you play the land on an opponent's turn.
You've got a lot going on and a huge number of effects you are trying to put into one set.
WG - Loyalty (This creature gets +1/+1 for each other creature with loyalty in play under your control).
Your deck only wants creatures with this ability but each one makes your whole team stronger, like a deck of all Muscle Slivers, so it will be tough to cost.
WU - Martyr (Whenever a spell or ability is put onto the stack, if that spell or ability could target this card but doesn’t, you may choose to have that its controller changes one of its targets to this card).
Sort of Flagbearer, but more powerful because you can choose for your opponent when the spell targets or doesn't.
WR - Auraflux X (X: Return this Aura card from your graveyard to play attached to target player or card it can enchant. Play this ability only once at your upkeep).
Mechanics that let you repeatedly replay the same card tend to be dangerous because they can lead to stagnant play patterns. See Flashback or Escape for mechanics that have balanced replaying the spell with limiting repetitiveness. Also, Red is the least enchantment friendly color so this is an odd choice for WR.
WB - Lifebound (At the beginning of your upkeep, if you have four or more creature cards in your graveyard, you may return one creature card with lifebound from your graveyard to your hand this way each turn).
Same issue as above, but does limit slightly the longterm repetitiveness.
GU - Sneak attack X (You may play this creature card from your hand by paying X. If you do, it has haste. Sacrifice it at the end of the turn).
This feels like a more punishing version of Dash, and a very aggressive mechanic like this feels very out of place in Blue.
GR - Fling X (X, Sacrifice this creature: This creature deals an amount of damage equal to its power to target creature or player).
Being able to hit players makes this mechanic VERY strong, as it basically lets you sit on defense until you have a critical mass and then deal your opponent 20. Also, direct damage to players isn't in Green's color pie, so at best these should only hit creatures or planeswalkers.
GB - Sentinel (When this card is put into a graveyard from play, remove it from the game. If you do, you may search your library for a card with the same name as this, reveal it and put it into your hand. Then shuffle your library).
Same repetitive play pattern issues as above to an extent. A lot of these keywords would work fine on one or two cards, maybe a cycle, but they aren't well suited to a whole keyword.
UR - Radiate X (As you play this spell, you can pay X. If you do, copy it for each other player or card the spell could target. Each copy targets a different one of those permanents or players).
Basically [card-Cyclonic Rift]Overload[/card], which is a solid spell mechanic.
UB - Necromagic — X, Remove this card in your graveyard from the game: This card does something.
Seems fine.
RB - Specter (When this creature comes into play from your hand, put a plane counter on it. As long as it has no plane counters on it, it cannot attack or block. When it would be put into a graveyard from play, if it has no plane counters on it, then remove it from the game instead. Otherwise remove it from the game instead and return that card to play under its owner’s control at the end of the turn).
If I'm parsing this right, a mechanic where you cannot attack with your creatures when you cast them is not a good fit for RB, being the most recklessly aggressive color combo. Also, need to be "enters the battlefield, if you cast it, put a plane counter on it." since most creatures enter the battlefield from the stack by being cast rather than directly from the hand. As written, it would only get the counter if you used Sneak Attack or something.
These do feel like Invasion era cards. There have been numerous wording and templating changes to how rules text is written, but I get the intention of the cards.
Mostly the issues tend towards things I described above. Take Helcaraxe, for instance. Every turn I can block, sac the enchantment to regenerate the creature and then replay the enchantment to do it again, which bogs combat down to nothing happening. And the most typical way for many colors to deal with Auras - killing the creature in response to the aura being cast, doesn't keep the aura from recurring.
It is odd having so many named characters without marking them as Legendary. I'm assuming that was an oversight.
Lothlorien needs to specify non-land permanents. If your opponent doesn't have an early play and you can hit them with this to put a land back in their hand, you are creating the most unfun play pattern in magic. This is why land destruction is now very limited and surgical about hitting land utility without disrupting the ability to cast spells.
Osgiliath doesn't work. Giving a land Flash does not actually let you play the land on an opponent's turn.
Your deck only wants creatures with this ability but each one makes your whole team stronger, like a deck of all Muscle Slivers, so it will be tough to cost.
Sort of Flagbearer, but more powerful because you can choose for your opponent when the spell targets or doesn't.
Mechanics that let you repeatedly replay the same card tend to be dangerous because they can lead to stagnant play patterns. See Flashback or Escape for mechanics that have balanced replaying the spell with limiting repetitiveness. Also, Red is the least enchantment friendly color so this is an odd choice for WR.
Same issue as above, but does limit slightly the longterm repetitiveness.
This feels like a more punishing version of Dash, and a very aggressive mechanic like this feels very out of place in Blue.
Being able to hit players makes this mechanic VERY strong, as it basically lets you sit on defense until you have a critical mass and then deal your opponent 20. Also, direct damage to players isn't in Green's color pie, so at best these should only hit creatures or planeswalkers.
Same repetitive play pattern issues as above to an extent. A lot of these keywords would work fine on one or two cards, maybe a cycle, but they aren't well suited to a whole keyword.
Basically [card-Cyclonic Rift]Overload[/card], which is a solid spell mechanic.
Seems fine.
If I'm parsing this right, a mechanic where you cannot attack with your creatures when you cast them is not a good fit for RB, being the most recklessly aggressive color combo. Also, need to be "enters the battlefield, if you cast it, put a plane counter on it." since most creatures enter the battlefield from the stack by being cast rather than directly from the hand. As written, it would only get the counter if you used Sneak Attack or something.