#additional costs

When you activate Goblin Test Pilot's ability, you choose from among legal targets for its ability during the activating process. If that target happens to be Kopala or anothehr Merfolk controlled by that player, then an additional cost of 2 is imposed on the costs of the ability. You're then free to pay it (and in fact must if you have 2+ mana in your mana pool), but if you don't have the mana in your mana pool, you're not forced to generate it.

Since you then can't pay the costs to activate the ability, the entire activation is undone. You're then free to try activating the Test Pilot again. You're free to do this until the Test Pilot targets a non-Merfolk target if you like, but if you go around abusing this interaction, expect to get some sour looks from the other players in your game.

Just recently postnord (the primary delivery service in sweden) put in effect a tax on any package coming from out of the EU equal to 7,50 euros. This means that if you for example buy something for one euro from eBay and it is shipped from Kina (as most things are) it will still cost you 8,50 euros (or 85 kronor). It is complete bullshit and I'm mad as hell at the fuckbags who thought this was a good idea especially since I just recently bought a couple of things from out of the EU for cosplay purposes (things I cannot send back). This means that I have to pay an additional 30 euros to the things I bought even though I didn't buy for more than 20 €, altogether it will cost me around 50 € (or 500 kr). It is a horrible abuse of e-commerce which at this point really is just a part of daily life.

I hope that they will fix this sometime soon, the backlash is already huge enough, but until then I just wanted to get this warning out to anyone in the habit of buying from out of the European borders, living in sweden.

Alternate costs? No.

Additional costs? Yes.

When you cast a spell without paying its mana cost, you're already paying an alternate cost of 0. Any time you're casting a spell and not paying the printed cost, that's an alternate cost and you can only ever pay one alternate cost to cast a spell.

So why can't you choose to overload Cyclonic Rift rather than casting it for free with Vadrok? That's because Vadrok's ability is what's allowing you to cast the spell at all, so you have to pay the alternate cost it dictates if you want to cast it.

Correct.

Any additional cost you choose to pay for Chorus of the Conclave becomes part of Hogaak’s total cost and as such is affected by its mana prohibition. Since it’s part of the total cost, though, you get to pay it with delve and convoke! Hooray!

Retrace is an additional cost you can pay in order to cast an instant or sorcery card with retrace from your graveyard. This cost is paid in addition the card’s mana cost, or an alternate cost if available, and that other cost must still be paid.

Wheel of Fate and other cards with no mana cost have an unpayable mana cost and thus can never be cast except for an alternate cost. Giving these cards retrace does nothing to allow you to cast them unless you can also give them an alternate cost in the graveyard as well.

When you cast a spell with replicate, you declare how many times you’re going to pay the replicate cost. The replicate cost is then added to the mana cost that many times before any cost reduction effects are applied and changes the total cost of the spell, but not the converted mana cost.

Any effect that reduces the cost of a spell will reduce the total cost once the replicate cost(s) have been added on, but there’s no way to discount each instance of replicate separately.

Sadly this pairing is a big fat non-bo.

Since Tithe Taker increased the cost of the otherwise free spell to 1, it’s no longer cast without mana being paid for it and so Lavinia won’t be able to counter it.

Tithe Taker’s ability just imposes an additional cost. It’s not a trigger and thus can’t happen after Lavinia’s ability.

Yes.

When you cast a spell with Kess, you’re not paying a set alternate cost, so you can choose any alternate costs the card might have. Any time you cast a spell with an optional additional cost, such as kicker or escalate, you always have the option to pay that cost.