Abyssal Specter, uncommon (first printed in Ice Age, 1995)

This is the accepted baseline for the Specter creature archetype and commonly not good enough to suit a seasoned competitive player - Hypnotic, Blazing and Sedraxis Specters await. Still, if you can look past its near-obsoletion by those three cards you'll find that the Abyssal one is still serviceable and more reliably resilient thanks to its extra point of toughness, resisting Pyroclasm, Sudden Shock and other popular zaps. That's probably not enough to make it your first pick in any scenario other than, well, Ice Age draft, but there's no reason to retire this card - he's still solid in any highlander or large-deck format you care to name. Can be acquired for about twenty pence in your choice of black or white borders, with various pictures to choose from over the years.

Abyssal Persecutor, mythic (first printed in Worldwake, 2010)

This is unacceptable. Here's the latest card in the WotC Mythic Series which make you feel wretched for being unable to afford and, noticeable by their absence, instantly brand your deck sub-optimal. It's a really powerful and undercosted card with no practical disadvantage to speak of, nor any nuance or elegance either in design or practise. Total trash; avoid infuriating your casual friends with this noticeably pushed card while sparing your competitive friends no opportunity to crash yours into theirs. Can be acquired for anywhere between fifteen and twenty pounds, I imagine, and good luck to you.