Its a 3/2 for four that can either blow up a creature or planeswalker, counter a spell, activated ability, or triggered ability
It is a great card to have in the cube, it has loads of nice synergies and it helps increase the overall consistency which in turn increases the overall quality of the games
(See?) An effect that allows you to put an artifact card from your graveyard onto the battlefield wouldn't affect Sword of the Realms, however: a modal double-faced card has only its front side's characteristics while in the graveyard
Niv-Mizzet, Guildpact While arguably not even in the top 3 or 4 Niv-Mizzets, Niv-Mizzet, Guildpact has one of the strongest saboteur abilities available
The problem is that a 2/2 (even a 2/2 with flying) can be outclassed fairly quickly, so delaying Vexing Gull trades its early game relevance (pecking in for damage) for mid-game value (when you might be behind in the race or not be able to attack with Vexing Gull)
Need that Counterspell